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AMERICAN    PRACTICE 


IN 


BLOCK    SIGNALING 


WITH  DESCRIPTIONS  AND  DRAWINGS  OF 
THE  DIFFERENT  SYSTEMS  IN  USE  ON 
RAILROADS  IN  THE  UNITED  STATES, 


1891: 
THE    RAILROAD    GAZETTE 


NEW     YORK. 


' 


- 


CONTENTS. 


Introduction, 

The  Simple  Block  System, 

The  Sykes  System, 

Single-Track  Blocking, 

Automatic  Clockwork  Track-Circuit  Signals, 

The  Eloctro-Pneumatic  Track-Circuit  System, 

The  Hall  Signal, 

Black's  Mechanical  Block  Signal, 


-A-  IF*  IE3  E  3ST  ID  I  ZXI    (Illustrated  descriptions). 


The  Sykes  Block  Signal  Apparatus, 

Automatic  Signals  on  the  Boston  &  Albany, 

The  Westinghouse  System  of  Pnu'ematic  Interlocking, 

Automatic  Block  Signals  on  the  Pennsylvania, 

Electric  Apparatus  for  Automatic  Block  Signals,     - 

Automatic  Signals  on  the  Fitchburg  Railroad, 

The  H&ll  Block  Signal, 

Hall  Block  Signals  on  the  New  York  Central, 

Black's  Automatic  Block  Signal, 

Illuminated  Semaphore  Signals, 

The  Koyl  Parabolic  Semaphore, 

The  Stewart-Hall  Train-Order  Signal, 


*•"••' 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 


INTRODUCTION. 

The  pages  which  follow  are  a  reprint  of  articles  which  appeared  in  the  Railroad 
Gazette  in  1890  and  previous  years.  It  was  the  purpose  to  give  in  those  articles  a  short 
description  of  the  methods  of  block  signaling  now  in  use  in  this  country,  summarizing 
the  salient  features  of  each  system.  It  was  not  within  the  scheme  of  the  articles  to  ex- 
haustively discuss  or  describe  principles,  methods,  or  appliances,  but  to  give  to  one 
comparatively  new  to  the  subject  a  fairly  good  grasp  of  it  in  general  and  in  detail,  and 
to  indicate  to  him  the  appliances  which  he  might  profitably  investigate  should  he  wish 
for  fuller  or  more  accurate  knowledge.  All  of  the  matter  up  to  page  22  is  substantially 
a  reprint  of  articles  published  in  1890,  although  a  few  alterations  have  been  made  to 
bring  the  information  up  to  date  (1891).  The  descriptions  of  apparatus  in  the  appendix 
were  published  at  various  times,  as  indicated  by  the  dates  attached  to  each. 

There  are  practically  two  systems  of  block  signaling,  of  which  we  may  call  the  first  the 
simple  block  system.  Assuming  that  every  railroad  is  properly  supplied  with  telegraph 
offices,  this  may  be  said  to  be  merely  a  code  of  rules  by  which  the  attendant  at  a  given 
station  exhibits  a  signal  to  hold  all  trains  moving  in  a  certain  direction  until  he  receives 
word  by  electrical  communication  that  the  last  preceding  train  has  reached  another 
station  and  gone  out  of  the  section  of  track  intended  to  be  protected.  This  is  an  absolute 
block  system.  When  the  regulations  permit  a  second  train  to  be  sent  over  the  road 
before  the  first  one  has  gone  out  of  the  block  section,  but  under  instructions  to  run 
slowly,  the  term  per  missive  blocking  is  used. 

The  signals  by  which  trains  are  admitted  to  the  sections  under  a  block  system  may  be 
electrically  connected  with  each  other  and  locked  by  the  Sykes  system,  so  that  when  an 
operator,  after  admitting  a  train  to  a  section,  puts  his  signal  to  danger,  the  lever  of  the 
signal  is  automatically  locked,  so  that  the  signal  cannot  again  be  lowered  (placed  in 
the  safety  position)  for  another  train  until  the  train  first  mentioned  has  actually  reached 
the  next  station  and  operated  an  electromagnet.  When  signals  are  fitted  with  these 
locks,  permissive  blocking  is  impracticable,  unless  (1)  the  operator  disconnects  the  wires 
by  which  the  Sykes  locks  control  the  signal  levers,  or  (2)  the  signal  is  left  in  the  danger 


2  INTRODUCTION. 

position  and  enginemen  are  instructed  by  flag,  lamp,  or  hand  signal  to  proceed  regard- 
less of  the  "regular  signal.  In  either  case  the  safeguard  provided  by  the  locks  becomes 
inoperative,  as,  when  two  trains  are  in  a  section,  the  first  passing  out  releases  the  signal 
so  that  a  third  may  be  admitted,  while  the  second  may  be  indefinitely  detained  within 
the  section. 

The  second  system  is  the  automatic.  In  this  no  attendant  is  provided,  but  each 
signal  stands  ordinarily  at  "all  clear"  to  admit  a  train  to  its  section.  The  train  on  enter- 
ing sets  the  signal  at  danger  by  the  operation  of  an  electric  circuit,  actuated  by  the 
passage  of  the  wheels,  and  resets  the  signal  at  "  clear"  when  it  emerges  from  the  section. 
The  first  automatic  signal  system  was  the  original  Hall,  which  was  used  in  Massachusetts 
and  Connecticut  about  1871.  In  this  the  electric  communication  from  one  station  to 
another  was  by  means  of  a  line  wire  strung  upon  poles.  Some  eight  or  nine  years  later  the 
track-circuit  system  was  introduced  on  the  Fitchburg  road  by  the  Union  Signal  Company 
In  this  the  electric  circuit  is  conducted  from  one  end  of  a  block  section  to  the  other 
through  the  rails  of  the  track  ;  and  the  proper  working  of  the  system  depends  upon  the 
integrity  of  this  circuit.  The  presence  in  the  section  of  even  a  single  pair  of  iron  wheels 
connected  together  by  an  iron  axle  allows  the  passage  of  the  electric  current  from  one 
rail  to  the  other,  and  withdraws  the  force  that  holds  the  signal  at  "clear."  If  a  train 
breaks  apart,  the  exit  of  a  portion  of  it  from  the  block  section  does  not  clear  the  signal  at 
the  entrance,  as  is  the  case  with  a  simple  line-wire  system. 

The  most  common  form  of  track  circuit  signal  is  that  in  which  the  signal  consists  of 
a  disc  operated  by  clockwork,  the  latter  being  controlled  by  the  electric  current.  In  the 
pneumatic  track-circuit  system  the  signal  consists  of  a  semaphore  operated  by  compressed 
air,  which  is  controlled  by  the  electric  circuit. 


THE  SIMPLE  BLOCK  SYSTEM. 

The  most  extensive  block  system  in  this  country  is  that  of  the  Pennsylvania  Rail- 
road, which  is  substantially  the  same  as  that  in  use  on  the  great  majority  of  the  railroads 
of  Great  Britain,  though  there  are  numerous  differences  in  the  detail  of  operation.  The 
Pennsylvania  uses  the  simple  block  system  (without  Sykes  locks).  When  the  system 
was  introduced  the  number  of  trains  had  already  grown  so  large  that  it  became  necessary, 
in  order  to  accommodate  them,  to  establish  stations  especially  for  signaling,  the  regular 
stations  being  too  far  apart.  These  intermediate  stations  are  generally  two-story  build- 
ings, and  are  termed  "towers"  ;  and  these  buildings,  being  characteristic  of  the  system, 
have  come  to  be  regarded  by  many  people  as  an  essential  part  of  it;  but,  in  point  of  fact,  many 
of  the  block-signal  operators  are  located  in  ordinary  station  offices.  On  those  sections  of 
the  Pennsylvania  where  trains  are  most  frequent  the  block  sections  are  from  one  to 
two  miles  long.  Near  large  terminal  stations  the  intervals  are  in  many  cases  considera- 
bly less  than  a  mile.  Regular  telegraph  stations  are  used  wherever  possible,  but  the 
larger  stations  have  to  have  two  telegraph  offices,  one  for  block  signaling  and  one  for 
ordinary  business.  Special  stations  are  established  between  the  regular  stations  at  such 
points  as  will  best  divide  the  space  and  maintain  an  approximately  uniform  length  of 
block.  On  portions  of  the  road  where  trains  are  less  frequent  the  sections  are  made 
longer,  in  some  cases  four  or  five  miles.  Each  station  has  a  fixed  signal.  This  con- 
sists of  a  semaphore  with  a  single  light,  which  shows  red  when  the  arm  of  the  semaphore 
is  at  "danger"  (horizontal)  and  white  when  the  arm  of  the  semaphore  is  dropped,  to 
indicate  '•  all  clear."  There  is  a  separate  semaphore  arm  for  each  track,  but  the  eastbound 
and  westbound  arms  are  generally  placed  on  one  post,  and  a  single  lamp  answers  for  both. 
The  older  form  of  signal  was  a  disc,  but  these  are  being  gradually  displaced  by  the  sema- 
phore, which  is  now  standard.  The  electrical  apparatus  consists  simply  of  a  Morse  tele- 
graph line,  with  the  usual  instruments.  On  the  passage  of  a  train  the  operator  places 
the  signal  at  danger  to  stop  following  trains,  and  reports  the  time  to  the  station  which  the 
train  last  passed  and  to  that  toward  which  it  is  proceeding. 

Summary  of  Pennsylvania  Joules. — A  block  section  is  called  a  "block."  Trains 
will  be  governed  absolutely  by  fixed  signals,  and  will  not  observe  the  time-space  rule. 
The  old  form  signal  has  a  green  disc  to  indicate  caution.  With  semaphores  a  position 
midway  between  horizontal  and  the  nearly  vertical  position  is  employed  to  indicate  cau- 


4  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

tion.  These  cautionary  indications  are  of  course  used  only  in  permissive  blocking.  The 
signal  normally  stands  at  danger.  After  being  changed  for  a  train,  it  must  be  returned 
to  danger  as  soon  as  the  whole  of  the  train  has  passed  the  signal.  A  train  mu*t  not  be 
backed  after  stopping  at  a  block  station.  In  case  of  failure  of  wires,  or  the  operator  for 
any  reason  cannot  get  orders  for  a  train,  he  must  give  it  written  notice  of  the  reason  for 
the  proper  signal  not  being  displayed.  Trains  must  not  be  admitted  to  a  block  section 
under  the  permissive  system  to  follow  a  passenger  train,  and  a  passenger  train  must  not 
be  admitted  to  follow  permissively  any  train  until  it  is  first  stopped  and  notified  that 
there  is  a  train  ahead.  Exceptions  are,  however,  made  to  the  last  paragraph.  A  train 
intending  to  use  a  crossover  between  the  block  stations  must  notify  the  operator.  A 
train  must  not  be  reported  as  having  passed  until  the  rear  end  has  got  300  ft.  beyond  the 
signal.  Trainmen  are  not  relieved  from  observing  all  ordinary  rules  in  regard  to  the  pro- 
tection of  their  train. 

The  customary  place  for  the  signal  is  immediately  opposite  the  telegraph  office. 
Where  this  is  at  a  passenger  station,  inconvenience  sometimes  results  from  the  fact  that 
the  train  held  by  the  signal  is  not  in  a  convenient  position  for  discharging  and  loading 
passengers.  To  provide  against  this  the  station  should  be  equipped  with  two  signals,  a 
"  home"  and  a  "  starting,  "  the  former  to  stop  trains  before  they  reach  the  station,  and 
the  latter  to  hold  trains  which  are  standing  at  the  station.  By  this  means,  if  the  block 
section  in  advance  is  occupied,  a  train  may  be  safely  admitted  to  the  station  while  yet  it 
is  kept  under  control,  so  that  it  cannot  leave  without  the  permission  of  the  operator.  If 
a  train  is  detained  at  the  station,  the  following  train  need  not  be  held  back  at  the  en- 
entrance  of  the  next  preceding  block,  one,  two,  or  more  miles  away,  but  may  be  allowed 
to  come  up  to  the  home  signal,  whence  it  can  proceed,  without  delay,  to  the  platform  as 
soon  as  the  one  in  advance  has  made  way  for  it. 

A  danger  in  signaling  is  the  possibility  of  trains  entering  the  main  track  from  a  siding 
or  at  a  crossover  track  midway  of  the  section  without  the  knowledge  of  the  operater  at 
the  entrance  to  the  section.  To  provide  against  this,  all  switches  connecting  with  such 
sidings  or  crossovers  should  be  under  the  control  of  the  operator.  This  may  be  effected 
by  an  electromagnetic  lock,  so  arranged  that  it  cannot  be  released  except  from  the  oper- 
ator' s  office,  the  latter  being  connected  with  the  switch  by  wire  ;  or  an  ordinary  switch 
may  be  locked  by  a  special  key,  which  must  be  obtained  from  the  block-signal  operator. 
Neither  of  these  systems  is  used  to  any  extent  in  the  United  States.  The  regulations  of 
the  Pennsylvania,  as  noted  above,  require  simply  that  a  conductor  intending  to  turn  a 
switch  between  two  block  stations  for  the  purpose  of  using  another  main  track  than  that 
on  which  he  belongs  must  notify  the  block  operator  beforehand,  and  get  his  acknowledg- 
ment, with  authority  to  so  use  the  track.  In  view  of  the  difficulty  of  controlling  these 
outlying  switches  satisfactorily,  an  essential  point  in  preparing  a  road  for  operation  under 
a  block  system  is  the  lengthening  and  alteration  of  side  tracks  so  that  as  many  as  pos- 


THE  SIMPLE  BLOCK  SYSTEM.  5 

sible  of  such  tracks  shall  connect  with  the  main  track  at  a  station — that  is,  between  two 
signals,  a  home  and  a  starting  signal,  which  are  controlled  and  handled  by  the  same 
operator. 

A  train  must  of  course  never  pass  a  block  signal  until  its  indication  is  absolutely 
known.  When  there  is  a  fog  or  a  driving  snowstorm,  or  the  signal  is  obscured  by  steam 
from  a  locomotive  or  any  other  cause,  a  fast  train  approaching  a  block  station  must  be 
slackened  in  order  to  permit  the  engineer  to  make  sure  of  the  indication  of  the  signal 
before  it  is  too  late  for  him  to  stop.  The  annoyance  from  numerous  delays  to  fast  trains 
from  this  cause  has  led  to  the  introduction  of  cautionary  signals,  erected  at  a  distance 
from  the  home  signal,  and  indicating  the  position  of  the  latter.  Home  and  distant  sig- 
nals generally  differ  in  color,  and  the  end  of  the  distant  signal  blade  is  notched.  Custom- 
arily the  positive  signal  blade  is  painted  red  and  the  cautionary  green.  The  light  on  the 
cautionary  signal  is  made  to  indicate  green  for  caution  and  white  for  "all  clear."  The 
cautionary  signals  are  erected  at  from  1,000  to  2,000  feet  from  the  home  signal.  If  an 
approaching  engineman  finds  one  of  them  in  the  "all  clear"  position,  he  knows  that 
the  home  signal  has  been  pulled  to  "all  clear,"  and  that  he  need  not  expect  to  be 
stopped  at  that  signal.  This  distant  (cautionary)  signal  must  of  course  be  interlocked 
with  the  home  (positive)  signal  so  that  it  can  never  by  mistake  be  pulled  to  safety  until 
the  positive  signal  has  actually  been  so  pulled. 

Illuminated  blades,  which  are  extensively  used  for  switch  signals  in  yards  (for  move- 
ments other  than  those  of  fast  trains  on  main  tracks),  have  been  used  to  a  limited  extent 
for  fast-route  signals,  and  are  equally  applicable  to  the  block  system.  The  term  "illumi- 
nated blade"  means  a  blade  in  connection  with  which  a  lamp  (hidden  from  the  engineer) 
is  attached  to  the  post  is  such  a  position  that  it  throws  light  directly  on  the  face  of  the 
blade.  The  engineman  can  thus  see  its  position  at  night  the  same  as  in  the  daytime,  and 
a  signal  lamp  is  unnecessary.  Illuminated  blades  are  prescribed  for  all  new  work  on 
the  Pennsylvania  lines  west  of  Pittsburgh,  and  the  standard  color  of  blades  there  is 
yellow.  By  this  means  the  color  indication  can  be  entirely  discarded. 

The  painting  of  arms  yellow  or  some  color  which  has  not  by  common  custom  received 
some  definite  significance  is  a  step  in  the  right  direction,  as  there  is  an  inconsistency  in 
painting  the  face  of  a  semaphore  arm  white  or  red,  because  it  must  indicate  when  hori- 
zontal, the  opposite  of  white,  and  when  down  the  opposite  of  red.  Green  being  gener- 
ally used  for  caution  gives  a  wrong  indication  when  the  arm  is  either  up  or  down. 

The  chief  fault  found  with  illuminated  blades  is  the  difficulty  of  making  them  visibl  e 
at  the  proper  distance.  To  overcome  this  the  Union  Switch  &  Signal  Co.  has  introduced 
a  blade  carrying  a  corrugated  reflecting  surface  of  brilliant,  non-corrosive  metal.  Koyl's 
parabolic  semaphore,  manufactured  by  the  National  Switch  &  Signal  Co.,  consists  of  a 
semaphore  arm  made  on  the  lines  of  a  section  of  a  parabola,  so  as  to  more  efficiently  re- 
flect the  rays  of  light  in  parallel  lines.  Both  these  signals  may  or  may  not  be  arranged 


6  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

so  as  to  throw  a  red  light  upon  the  blade  when  it  is  in  the  horizontal  position,  and  a 
white  light  when  it  is  pulled  down.  These  devices  are  familiar  to  those  who  have  followed 
the  progress  of  the  art  in  the  columns  of  the  Railroad  Gazette,  and  are  described  in  de- 
tail in  the  appendix. 

Cost  of  Maintenance. — The  principal  item  of  cost  is  of  course  the  wages  of  opera- 
tors and  inspectors,  to  which  is  to  be  added  the  maintenance  of  buildings,  with  fuel  and 
lights,  where  a  building  is  erected  especially  for  this  service.  At  stations  where 
operators  have  no  switches  to  attend  to,  and  no  other  work  of  any  kind,  they  work  12 
hours  each  per  day,  seven  days  in  the  week.  The  pay  of  these  men  is  from  $45  to  $55 
per  month.  Where  the  duties  are  more  complex  the  pay  is  higher,  and,  where  a  con- 
siderable number  of  interlocking  switches  is  operated,  the  working  time  for  each  man  is 
eight  hours  daily.  The  men  at  these  important  towers  are  paid,  on  the  Pennsylvania, 
from  $50  to  $70  per  month.  On  the  New  York,  Lake  Erie  &  Western  some  of  the 
operators,  who  work  12  hours  daily,  alternate  weekly  between  day  and  night  work. 
The  duties  of  the  inspectors  are  light,  so  far  as  'simple  block  stations  are  concerned. 
Their  work  is  chiefly  in  connection  with  interlocking  towers,  which  at  all  important 
stations  are  operated,  as  intimated  above,  by  the  same  man  who  attends  to  the  block 
signaling,  and  the  time  spent  inspecting  simple  block  stations  is  treated  as  a  secondary 
matter.  For  more  detailed  estimates  of  expense  the  reader  is  referred  to  a  subsequent 
chapter  on  the  Sykes  system.  As  in  the  system  here  described  the  cost  of  inspection  is 
but  a  very  small  fraction  of  the  total  expense,  and  as  the  latter  must  depend  upon  con- 
ditions which  must  be  calculated  in  each  case  by  itself,  farther  consideration  of  the  sub- 
ject here  is  unnecessary.  A  recent  estimate  on  a  prominent  road  showed  that  100  miles 
of  its  line  could  be  worked  under  the  block  system,  with  block  sections  four  miles  long, 
by  the  erection  of  only  three  towers  between  regular  stations.  When  it  is  considered 
that  trains  running  at  40  miles  an  hour  and  on  10-minute  intervals  are  6f  miles  apart, 
the  possibilities  of  the  block  system  will  be  readily  recognized. 

The  West  Shore,  the  Chicago,  Burlington  &  Quincy  and  the  New  York,  Lake  Erie 
&  Western  are  the  principal  roads,  outside  those  controlled  by  the  Pennsylvania,  which 
use  the  block  system  as  above  described.  Others  use  it  on  very  short  sections  of  road  or 
for  only  a  portion  of  the  trains.  It  is  scarcely  necessary  to  say  that  this  system  has 
given  full  satisfaction  wherever  used.  No  officer  on  a  road  using  it  ever  thought  of 
abolishing  it  or  of  diminishing  its  use  in  any  way.  Operators  have  admitted  a  train  to  a 
section  when  it  was  not  clear,  and  engineers  have  disregarded  danger  signals,  causing 
collisions  ;  but  the  excellent  record  on  the  Pennsylvania,  where  the  system  has  been  in 
operation  on  500  miles  of  double  track  for  over  ten  years,  shows  that  these  defects  of 
discipline  are  not  to  be  regarded  as  incurable.  The  first  step  toward  abating  them  by 
mechanical  means  is  the  adoption  of  the  Sykes  system,  which  we  shall  next  consider. 


THE  SYKES  SYSTEM.* 

The  most  common  lorm  of  electric  locking,  as  an  additional  safeguard  to  be 
used  in  connection  with  the  block  system  is  that  known  as  the  Sykes  system.  In 
fact,  this  is  the  only  apparatus  of  the  kind  yet  put  in  use  in  this  country.  It 
is  in  use  on  the  New  York,  New  Haven  &  Hartford,  the  New  York,  Lake  Erie  & 
Western  and  the  New  York  Central  &  Hudson  River.  The  latter  company  has 
only  about  18  miles  of  road  equipped  with  this  apparatus  (all  in  New  York  City);  but  as 
the  system  has  here  been  in  use  longer  than  on  either  of  the  other  roads  named,  and  las 
to  meet  the  most  trying  conditions,  we  shall  base  our  description  on  the  information  given 
by  officers  of  this  road.  The  New  York  Central  allows  no  permissive  blocking  whatever 
where  the  Sykes  instruments  are  in  use. 

The  apparatus  consists  essentially  in  a  series  of  electromagnets  so  connected  with 
the  levers  by  which  the  operator  moves  the  outdoor  signals  that  the  operator  at  the  out- 
going end  of  a  block  section  controls  the  lever  by  which  the  operator  at  the  incoming 
end  admits  the  trains.  Thus  after  A  sends  a  train  to  £  and  puts  his  signal  at  danger, 
he  is  unable  to  again  pull  the  signal  to  "all  clear  "  until  B  unlocks  his  (A's}  lever,  and 
B  of  course  refuses  to  do  this  until  the  train  has  arrived  and  passed  out  of  the  section. 
To  provide  against  a  possible  mistake  by  B,  who  might  prematurely  unlock  A' a  lever, 
there  is  also  an  automatic  arrangement  by  which  A's  lever,  after  having  been  put 
through  the  motions  to  admit  a  train,  cannot  be  unlocked  until  the  train  itself  actually 
passes  out  of  the  section.  This  is  secured  by  running  an  electric  circuit,  which  controls 
A's  lever,  through  two  or  three  rail  lengths  of  the  track  at  a  point  just  beyond  B.  The 
circuit  goes  from  the  battery  to  one  rail  of  the  insulated  section  of  track,  thence  by  line 
wire  to  A's  signal,  which  it  holds  locked  at  danger  by  energizing  an  electromagnet.  On 
the  passage  of  a  pair  of  wheels  over  these  insulated  rails,  the  circuit  is  led  through  the 
wheels  and  axles  from  one  rail  to  the  other  and  thence  back  to  the  battery  without  going 
to  the  electromagnet  at  the  distant  station,  thus  demagnetizing  that  instrument  and 
allowing  the  signal  to  be  again  operated. 

It  will  be  seen  that  where  trains  are  run  permissively — that  is,  where  a  second  train 
passes  A  before  the  first  one  has  passed  B — the  automatic  feature  of  this  system  becomes 
useless,  as  the  first  train  will  release  A's  signal  while  the  second  train  is  still  in  the  sec 

*  Drawings  and  detailed  description  are  given  on  page  22. 


8  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

tion,  and  the  apparatus  will  then  afford  no  protection  against  a  careless  operator  admitting 
a  third  train  to  the  section  before  the  second  has  cleared  it. 

One  section  of  seven  miles  of  double  track,  on  which  there  are  seven  stations,  was 
equipped  by  the  New  York  Central  in  1882.  The  cost  of  this,  including  two  interlocking 
machines  for  handling  three  switches  and  six  switches,  respectively,  was  $8,300,  of  which 
$2,050  was  for  the  seven  cabins  and  25  semaphores.  The  cost  of  operating  these  seven 
stations  is,  per  year : 

Salaries  of  cabin  men $9,480 

Salary  of  electrician 1,000 

Four  men  attending  signal  lights 1,920 

Cost  of  repairs  (estimated) 1,000 

..  $13,400 

This  estimate  would  be^o-Mgh.for  a  system  comprising  many  stations,  as  the  salary 
and  wages  account  wouj<iabe'  distributed  ^ve.r*j  more  stations.  On  another  road  the  cost 
of  maintaining  24  statiprif  using  Sykes  loyks.was  estimated  at  $3,043  per  year,  divided  as 
follows:  \  .  x  V  ''.;•*  *\  „•• 

^ \kl-.          .  * 

Battery  supplies „.*.- .•.'.*...•. $    153 

Battery  men  and  inspector  of  electrical  apparatus 1,440 

Ordinary  inspector  (occupied  partly  with  other  duties)  300 

Miscellaneous  repairs,  materials,  paint,  etc 150 

Deterioration  (estimated)    1,000 

$3,043 

This  of  course  does  not  include  the  wages  of  the  operators,  who  in  this  case  have 
at  many  o«f  the  stations  other  duties  to  perform. 

If  we  add  the  salaries  of  the  operators  to  this  estimate,  the  average  cost  per  station 
per  year  will  be,  in  round  numbers  : 

Two  operators  (day  and  night),  at  $55  each  per  month $1,320.00 

Battery  supplies ..., 6.50 

Inspectors 72.50 

Miscellaneous  repairs 6.50 

Deterioration 41.50 

$1,447.00 

This  takes  no  account  of  lamp  lighters.  Where  there  are  no  distant  signals  the 
operator  can  generally  light  the  lamps  himself.  In  both  the  cases  cited  there  are  but  few 
distant  signals.  Where  these  are  near  regular  stations  the  work  of  attending  to  the  lamps 
can  be  economically  devolved  upon  the  man  who  attends  to  the  ordinary  switch  lamps. 
The  expense  chargeable  to  block  signaling  for  this  service  is  to  be  added  to  the  total  above 
given  ($1,447),  while  on  the  other  hand  this  sum  can  be  diminished  by  an  amount  equal 
to  such  portion  of  the  operators'  salaries  as  can  be  fairly  charged  to  ordinary  station 
work. 

The  Sykes  instruments,  like  most  other  electromagnetic  devices,  require  constant  and 


THE  SYKES  SYSTEM.  9 

careful  inspection.  One  inspector  has  told  us  that  from  a  careful  record  he  found  his 
instruments  to  fail  once  in  20  days.  He  did  not  give  the  number  of  trains,  but,  as  the 
causes  of  the  failures  were  mostly  on  account  of  inadequate  inspection  or  too  infrequent 
renewal  of  battery,  he  had  no  doubt  that  by  the  increase  of  his  force  of  inspectors  he 
could  reduce  these  failures  to  practically  nil.  On  another  section,  where  he  was  able  to 
provide  sufficient  men  to  look  more  carefully  after  the  apparatus,  a  number  of  signals 
had  been  worked  under  a  very  heavy  traffic  for  more  than  a  year  without  a  single  failure. 


k£     .  *  I 


SINGLE-TRACK  BLOCKING. 

Within  the  past  seven  years  a  number  of  railroads  have  introduced  the  block  system 
on  single-track  lines,  modifying  the  regulations  somewhat  to  conform  to  the  different 
conditions.  This  system,  as  used  on  the  Canadian  Pacific,  was  described  in  the  Railroad 
Gazette  of  Dec  2,  ]  887.  Its  operation  on  a  division  of  the  Chicago,  Milwaukee  &  St. 
Paul  was  described  June  22, 1888,  and  the  same  system,  with  a  novel  arrangement  of  tele- 
graph wires  and  sounders,  as  used  on  the  Chicago  &  Council  Bluffs  division  of  that  road, 
was  described  in  the  issue  of  Jan.  17,  1890.  An  account  of  the  system  as  employed  on  the 
Wabash  was  given  Feb.  8, 1889.  The  salient  feature  of  these  applications  is  the  moderate 
cost,  which  has  been  reduced  to  a  minimum.  There  are  several  cases  in  the  United  States 
in  which  the  trains  both  ways  on  a  single-track  road  aggregate  more  than  the  trains  one 
way  on  most  double-tracks;  but  naturally  a  single-track  road  has  fewer  trains  than  a  double- 
track  line,  and  in  nearly  or  quite  every  case  the  improved  system  has  been  put  into  effect 
wholly  by  the  employment  of  regular  station  operators,  no  towers  being  established,  and 
the  only  important  additional  expense  being  the  employment  of  night  operators  at  some 
stations  where  otherwise  the  office  would  be  kept  open  only  during  the  daytime.  There  is 
no  practical  difficulty  in  making  this  system  as  effective  as  the  regular  double-track  block, 
but  most  or  all  of  the  companies  using  it  have  put  it  in  as  a  necessity,  and  have  not  felt 
able  to  incur  the  expense  of  new  signals,  carefully  located  for  purposes  of  block  signaling, 
of  distant  signals  and  of  protection  for  sidetracks  and  other  facing- point  switches  between 
stations.  They  have  treated  the  block  system  essentially  as  an  adjunct  of  the  train- 
dispatching  system.  While  by  no  means  perfect,  there  can  be  no  question  that  the  sys- 
tem is  a  valuable  safeguard  against  rear  collisions.  Assuming  that  conductors  and 
engineers  are  properly  disciplined  so  as  not  to  depend  upon  the  system  for  protection 
against  dangers  which  it  does  not  pretend  to  cover,  its  value  as  a  substitute  for  the  uncer- 
tain flagging  system,  especially  in  cold  and  stormy  weather,  is  undoubted. 

The  rules  under  which  this  system  is  operated  vary  considerably  on  the  different 
roads  named,  as  will  be  seen  by  reference  to  the  accounts  cited  above.  One  of  the  most 
valuable  rules  in  connection  with  this  plan  of  working  is  that  which  requires  inferior- 
class  trains  to  time  themselves  so  as  to  be  wholly  out  of  a  block  section  before  the  time 
at  which  a  superior-class  train  is  due  to  enter  it.  Another  is  that  which  provides  that 
when  a  train  is  to  take  a  sidetrack  at  a  station  the  operator  must  not  open  the  block 


SINGLE-TRACK  BLOCKING.  11 

for  another  train  until  this  one  has  completely  cleared  the  main  track.  All  the  roads 
named,  we  believe,  employ  the  ordinary  train-order  signal  for  stopping  and  starting 
trains,  though  the  Chicago,  Milwaukee  &  St.  Paul  has  a  semaphore  for  block  signaling 
and  one  of  the  old-style  disc  signals  for  train  orders.  The  use  of  two  danger  signals  at 
the  same  station  would  seem  to  be  of  questionable  expediency,  as  locomotive  runners 
would  probably  be  as  likely  to  overlook  one  of  the  signals  as  an  operator  would  be  to 
make  a  mistake  in  using  one  signal  for  1rwo  purposes.  A  number  of  roads  which  use  the 
block  system  on  single-track  allow  train  dispatchers  discretion  in  suspending  rules  dur- 
ing clear  weather  and  on  portions  of  the  road  free  from  curves,  when  traffic  can  be  has- 
tened thereby;  and  these  rules  are  used  temporarily  during  fog  or  severe  snow  storms  on 
a  good  many  miles  where  the  companies  have  not  yet  seen  their  way  clear  to  incur  the 
necessary  expense  of  their  constant  operation. 

On  the  Canadian  division  of  the  Michigan  Central  passenger  trains  are  kept  one  or 
more  stations  apart  by  the  regular  train-order  system,  the  dispatcher  giving  a  special 
written  order  to  the  operator  in  regular  form  for  each  operation;  and  this  system  is  ex- 
tended to  freight  and  other  trains  during  fogs  and  snow  storms. 

Cost  of  Operation. — As  intimated  above,  there  is  generally  no  special  item  of  ex- 
pense connected  with  this  system,  except  the  employment  of  additional  operators.  The 
Wabash  employed  three  at  $45  each  per  month  on  a  section  of  20  miles.  The  Chicago, 
Milwaukee  &  St.  Paul  added  six  on  a  section  of  130  miles.  On  this  130  miles  the  cost  of 
new  semaphores  and  a  line  wire  with  electromagnets  (sounders)  of  a  special  form  was 
$30  per  office,  these  averaging  four  miles  apart. 

A  recent  letter  from  a  Wabash  officer  gives  details  of  operation  of  the  system  on  a 
20-mile  section  of  that  road  which  were  not  fully  explained  in  the  article  above  referred 
to.  We  quote  a  paragraph: 

"When  a  train  passes  a  station,  the  operator  reports  the  time,  and  adds,  '  signal  out.' 
This  report  is  watched  for  by  the  operator  at  the  station  the  train  previously  passed, 
and  he  then  responds  'signal  in,'  releasing  the  block.  The  dispatchers  overhear  these 
reports,  and  know  always  that  the  proper  responses  are  being  made,  but  the  operators 
are  so  trained  that  it  is  not  necessary  to  call  them  to  release  the  block  after  the  train 
has  passed  the  next  station.  There  has  not  been  a  single  occasion  when  it  was  found 
necessary  to  suspend  the  operation  of  this  system  in  order  to  avoid  delays.  It  is 
true  that  some  delays  to  trains  occurred  by  reason  of  the  use  of  the  system,  but  we  have 
had  no  accidents,  although  it  is  a  very  busy  piece  of  the  road;  as  high  as  60  trains  a 
day  being  moved  over  the  20  miles  of  single  track  between  Decatur  and  Bement.  I  know 
of  no  instance  where  an  operator  has  made  a  mistake,  or  permitted  a  train  to  go  into 
a  section  when  it  was  dangerous  to  do  so." 

This  correspondent  refers  to  delays.  These  cannot  be  accurately  compared,  as  be- 
tween a  time-interval  and  a  distance-interval  system  of  spacing  trains  ;  but,  as  every  one 


12  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

knows,  the  efficiency  of  a  block -system  as  a  means  of  running  trains  close  together  de- 
pends wholly  upon  the  length  of  the  block  sections.  On  the  Wabash  they  are  about  four 
miles  long.  With  stations  half  a  mile  apart,  eight  times  as  many  trains  could  be  run,  and 
with  perfect  safety,  at  any  speed,  provided  a  caution  signal  were  erected  at  a  sufficient 
distance  from  each  block  signal  to  allow  a  train  to  be  got  "under  control"  before  it 
reached  the  block  signal. 

Although  the  Canadian  Pacific  was  the  first  road  whose  single-track  block  system 
was  brought  prominently  before  the  railroad  public,  the  eastern  division  of  the  Lake 
Shore  &  Michigan  Southern  seems  to  have  been  the  pioneer  in  this  respect,  and  we  there- 
fore add  here  an  extract  from  a  letter  from  one  of  the  officers  of  that  road  : 

"We  have  used  for  the  last  fifteen  years  positive  block  on  passenger  trains  following 
each  other,  only  allowing  one  train  between  the  same  stations  at  the  same  time.  We  only 
use  positive  block  on  freight  trains  during  foggy  and  stormy  weather.  The  positive  block 
on  passenger  trains  is  solely  in  the  hands  of  the  telegraph  operators,  but,  at  the  same 
time,  the  train  dispatchers  oversee  the  work,  and  see  that  it  is  done  properly.  The  posi- 
tive block  on  freight  trains  is  in  the  hands  of  the  train  dispatcher,  to  whom  the  state  of 
the  weather  is  given  everj7  hour,  and  on  whose  judgment  the  necessity  for  the  use  of 
positive  block  depends.  If  a  fog  or  snow  storm  should  suddenly  come  up,  the  operators 
immediately  notify  the  train  dispatcher,  whether  it  is  the  regular  time  to  report  or  not. 
If  the  train  dispatcher  directs  the  use  of  positive  block  for  freight  trains,  then  it  is  wholly 
in  the  hands  of  the  telegraph  operators,  under  the  same  conditions  as  the  passenger  trains. 
The  same  rules  also  apply  to  trains  on  double  track." 


AUTOMATIC  CLOCKWORK  TRACK-CIRCUIT  SIGNALS.* 

The  most  common  form  of  automatic  block  signal  in  this  country  is  the  Union  Switch 
&  Signal  Company's  "  Union  system."  This  system  is  in  use  on  the  Boston  &  Albany, 
Old  Colony,  New  York,  Providence  &  Boston  and  a  number  of  other  roads.  The  same 
apparatus  is  used  on  these  and  many  other  roads  as  a  station  signal ;  but  these  applica- 
tions should  not  be  confounded  with  the  block  system,  as  in  nearly  every  case  there  is 
only  one  signal  at  a  station,  and  the  regulations  under  which  it  is  used  make  it  a 
cautionary  signal. 

The  arrangement  of  the  apparatus  in  this  system  is,  briefly,  as  follows :  The  battery 
is  placed  underground  (or  in  any  position  where  it  is  protected  from  freezing)  at  the  out- 
going end  of  a  section,  and  from  this  the  electric  current  is  conducted,  through  one  of 
the  rails  of  the  track,  to  the  signal  at  the  incoming  end  of  the  section;  thence,  after  pass- 
ing through  the  signal  relay,  it  returns  to  the  battery  through  the  opposite  rail.  At 
switches  the  current  is  led  through  a  circuit  breaker  which  is  opened  whenever  a  switch 
rail  is  moved  so  as  to  break  the  main  track.  The  circuit  is  also  led  through  the  rails  of 
side  tracks  for  a  short  distance,  so  that  a  train  entering  a  side  track  is  protected,  the 
same  as  when  on  the  main  track,  until  all  its  cars  are  fully  clear  of  the  main  line.  The 
signal  itself  is  a  disc  fixed  to  a  vertical  spindle,  with  which  it  is  made  to  turn  one-quar- 
ter of  a  revolution  every  time  the  circuit  is  opened  or  closed.  The  turning  is  effected  by 
clockwork,  actuated  by  a  weight,  which  has  to  be  periodically  wound  up.  A  lamp  fixed 
to  the  upper  end  of  the  spindle  gives  the  same  indications  as  the  disc.  The  electric  cur- 
rent flowing  through  the  rails  does  not  operate  the  disc  directly,  but  by  means  of  a  relay 
opens  and  closes  a  more  powerful  local  circuit  which  starts  the  clockwork.  The  opera- 
tion of  the  signal  is  simple,  the  presence  of  a  pair  of  wheels  on  the  track  in  any  portion 
of  the  block  section  serving  to  devitalize  the  electromagnet  which  holds  the  signal  at  "  all 
clear."  This  condition  continues  as  long  as  the  train  or  any  portion  of  it  is  in  the 
section. 

The  signal  post  is  placed  about  100  or  150  feet  within  the  block  section,  so  that  an 
engineman  on  approaching  it  and  finding  it  "all  clear"  may  see  it  change  to  danger  (for 
the  protection  of  his  own  train).  If  it  fails  to  move  from  white  to  red,  he  knows  that 

*  Drawings  and  detailed  description  are  given  on  page  30. 


14  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

some  part  of  the  apparatus  is  out  of  order,  and  he  must  then  assume  that  there  is  danger 
ahead. 

By  a  proper  combination  of  relays  and  by  the  use  of  a  section  of  line  wire  (on  poles) 
the  signal  for  each  block  section  may  be  so  arranged  that  it  will  not  be  restored  to  "all 
clear"  until  the  train  has  passed  several  hundred  feet  beyond  the  outgoing  end  of  the 
section,  thus  providing,  in  effect,  a  distant  signal. 

The  roads  using  these  signals  give,  in  general,  very  favorable  reports  of  their  be- 
havior. Reports  made  to  railroad  commissioners  and  other  official  bodies  have  given 
detailed  records  of  the  number  of  stops  occasioned  by  the  signals,  subdividing  the  lists 
into  those  caused  by  a  preceding  train  in  the  section,  switch  misplaced,  broken  rail, 
failure  of  battery  or  instruments,  carelessness  of  custodians  or  inspectors  and  other  con- 
tingencies; but  the  records  available  show  such  widely  divergent  results  that  they  cannot 
be  regarded  as  a  proper  basis  upon  which  to  form  an  opinion.  Many  of  the  failures  and 
delays  were  the  direct  result  of  inexperience  or  lack  of  proper  supervision.  The  practical 
question,  however,  with  regard  to  stops  caused  by  imperfect  operation  of  any  automatic 
signal,  is,  how  numerous  and  how  serious  will  be  the  delays  to  trains  ?  And  the  remedy 
for  these  faults  lies  in  constant  and  careful  inspection  and  great  care  in  securing  the 
very  best  material  and  workmanship.  The  difficulties  in  this  direction  have  not  been 
entirely  overcome,  as  is  evident  from  the  changes  in  the  methods  and  means  of  taking 
care  of  signals  ;  but  that  the  results  are  in  general  satisfactory  is  evidenced  by  the  erec- 
tion of  new  signals  by  those  roads  which  have  tried  them  the  most  carefully.  The  Boston 
&  Albany  is  now  completing  the  equipment  of  a  whole  division  of  54  miles,  and  other 
New  England  roads  use  them  largely  and  with  satisfaction.  The  Union  Switch  &  Signal 
Co.,  however,  regards  its  electro-pneumatic  system  (with  semaphores)  as  so  greatly 
superior  to  the  clockwork  system  that  it  takes  no  special  pains  to  spread  the  use  of  the 
latter. 

The  possibility  that  track  circuit  signals  may  indicate  safety  when  danger  exists, 
which  is  a  vital  question  with  all  automatic  signals,  will  be  discussed  hereafter  in  con- 
nection with  the  pneumatic  system. 

A  point  in  favor  of  the  clockwork  signals,  which  is  regarded  as  important  by  some 
experts,  lies  in  the  fact  that  the  day  signal  is  a  disc  and  not  a  semaphore.  All  automatic 
systems  must  make  some  provision  for  releasing  a  train  when  the  signal,  through  some 
accident  or  mishap,  stops  it  while  the  track  is  in  fact  clear.  The  common  way  of  doing  this 
is  to  require  trains  to  come  to  a  full  stop,  and  then,  after  one,  two,  three,  or  any  prescribed 
number  of  minutes,  to  proceed  under  control  through  the  section.  To  do  this  the  engineer 
must  pass  the  signal  while  it  stands  at  danger.  If  such  unnecessary  stops  occur  fre- 
quently, engineers,  becoming  habituated  to  passing  signals  standing  at  danger,  will  be 
liable  to  carelessly  pass  danger  signals  in  yards  and  at  other  points  where  discipline 
imperatively  requires  that  a  train  shall  never  pass  a  signal  showing  danger.  But  with  all 


AUTOMATIC  CLOCKWORK  TRACK-CIRCUIT  SIGNALS.  15 

such  yard  signals  made  in  semaphore  form,  and  all  automatic  block  signals  made  in  disc 
form,  it  is  argued  that  the  engineer  need  not  fall  into  the  careless  habit  mentioned, 
because  the  differing  forms  will  always  be  a  guide  to  him  in  deciding  their  different 
degrees  of  importance. 

One  of  the  roads  using  this  system  has  given  us  the  following  memoranda  concerning 
cost  of  erection  and  maintenance.  Sixteen  signals,  covering  16  blocks  in  which  were  36 
switches,  cost  $8, 076.54.  This  is  divided  as  follows: 

16  signals  at  $300 $4,800.00 

36  switch  connections  at  $40 1,440  00 

Labor,  signals,  average  $96.78  each 1,548.54 

Labor,  switches,  at  $8  each  —  '. 288.00 


$8,076.54 

On  one  section  containing  83  signals,  all  within  a  territory  11  miles  in  length,  the 
expenses  for  maintenance  for  one  year  were  $7,062.67.  Of  this,  material  and  supplies  are 
charged  $2,831.85,  and  labor  and  superintendence  $4,230.82.  This  makes  a  total  of  $85.09 
per  signal  per  year.  On  another  section  160  signals  cost  for  one  year  $86  91  per  signal. 
This  last  included  important  renewal  work  (10  miles  of  new  poles  and  a  large  amount  of 
underground  wire). 

On  another  road  the  expense  of  maintenance  was  estimated  at  $90  per  signal  per  year, 
the  employment  of  the  inspectors  on  other  work  for  a  considerable  portion  of  their  time 
making  a  more  accurate  estimate  impossible. 


THE  ELECTRO-PNEUMATIC  TRACK-CIRCUIT  SYSTEM.* 

The  main  difference  between  the  apparatus  of  these  signals  and  that  of  the  clock- 
work signals  is  in  the  motive  power  and  the  form  of  the  signal.  In  the  pneumatic  system 
the  signal,  which  is  a  semaphore,  is  cleared  by  compressed  air  and  goes  to  danger  by 
gravity.  The  compressed  air  is  supplied  to  the  various  signals  by  a  pipe  running  along- 
side the  track,  a  stationary  steam  engine  or  other  power  for  compressing  air  being 
located  at  a  central  point  where  it  can  supply  a  number  of  signals.  Pneumatic  signals 
were  used  on  the  West  Shore  road  as  early  as  1883,  but  the  system  there  was  abandoned 
principally  because  the  pipes  for  conveying  compressed  air,  and  other  details,  were  not 
properly  maintained.  When  the  time  came  for  renewing  the  apparatus  the  prosperity 
of  the  railroad  company  had  declined  and  no  action  was  taken. 

The  electro-pneumatic  semaphore  has  also  been  in  use  on  the  Fitchburgh  road  since 
1883,  and  its  operation  there  was  described  in  the  Railroad  Gazette  of  June  15, 1888. 

The  latest  form  of  electro-pneumatic  signal  was  described  in  the  Railroad  Gazette 
of  Dec.  21,  1888,  and  Aug.  23  and  Sept.  6,  1889.  These  improved  signals  are  in  use  on 
the  Pennsylvania  road  east  of  Pittsburgh,  where  six  miles  of  four-track  line  have  been 
operated  for  about  two  years,  and  a  portion  of  it  since  1884.  The  officers  of  the  road  say 
that  these  signals  have  given  them  no  trouble  whatever.  Seven  miles  of  the  four-track 
line  of  the  New  York  Central  &  Hudson  River,  between  138th  street  and  Woodlawn, 
New  York  City,  are  being  equipped  with  this  system,  and  it  was  put  in  use  last  year  on 
seven  miles  of  the  Central  of  New  Jersey. 

This  system,  as  operated  at  the  places  named,  embraces  important  features  not  yet 
employed  in  any  other  automatic  signals,  and  the  plan  is  in  many  respects  an  ideal  one. 
The  signal  is  a  semaphore.  It  is  placed  exactly  at  the  entrance  of  a  block,  and  therefore 
does  not  turn  to  danger  in  the  face  of  the  engineer.  There  is  a  distant  signal  for  each 
home  signal.  Each  block  section  is  worked  with  a  single  circuit,  and  the  distant  signal 
is  controlled  by  a  wire  circuit  upon  poles. 

It  has  been  regarded  as  an  important  principle  in  automatic  signaling  that  the  loco- 
motive engineer  should  witness  the  operation  of  the  signal  as  he  passed  it,  thus  having 
constant  evidence  that  the  signal  is  in  working  order.  The  location  of  the  signal  precisely 

*  Drawings  and  detailed  description  are  given  on  pages  45,  46  and  49. 


THE  ELECTRO-PNEUMATIC  TRACK-CIRCUIT  SYSTEM.  17 

at  the  entrance  of  the  section,  as  is  the  case  with  the  pneumatic  signal  on  the  Pennsylvania, 
makes  this  inconvenient,  if  not  impossible,  as  it  is  hardly  to  be  regarded  as  expedient,  even 
if  it  were  practicable,  to  require  an  engineer  to  turn  around  and  look  at  a  signal  after  he 
has  passed  it.  By  the  enforcement  of  adequate  discipline  the  brakemen  of  a  train  could, 
however,  be  utilized  as  monitors  for  this  purpose  ;  and  we  understand  that  something  of 
this  kind  is  done  on  the  Pennsylvania.  This  is,  however,  a  question  of  practice.  There  is 
no  reason  why  the  electro-pneumatic  signals  or  any  automatic  signals  cannot  be  placed 
in  advance  of  the  entrance  to  the  seection  if  desired. 

The  track  circuit  system  is  an  ideal  automatic  block  signal  system.  It  promises  more 
complete  protection  than  is  possible  with  any  other.  The  electro-pneumatic  system  as 
now  in  operation  on  the  Pennsylvania,  New  York  Central  and  Central  of  New  Jersey  is 
the  highest  development  yet  reached  by  the  track  circuit ;  but  any  track-circuit  system 
requires  not  only  perfect  construction,  but  the  most  careful  maintenance.  Of  course  the 
most  serious  failure  of  any  automatic  signal  is  when  it  indicates  safety  when  it  should 
show  danger.  We  have  heard  of  a  few  such  failures  of  the  electro- pneumatic  signals. 
We  would  not  say  that  these  false  indications  have  come  from  unavoidable  defects  in 
the  system.  On  The  contrary,  there  are  no  stronger  advocates  of  the  electro-pneumatic 
system  than  those  who  have  used  it  most. 

If  an  automatic  signal  stands  at  safety,  and  fails  to  change  when  the  train  passes  it, 
the  engineer  must,  according  to  the  rules,  proceed  cautiously ;  but  by  this  reduction  of 
speed  the  train  loses  time  and  the  next  following  train  may  soon  be  too  close  upon  it.  If, 
on  the  arrival  of  this  second  train,  the  condition  of  the  apparatus  has  undergone  a  change, 
so  that  the  signal  changes  from  safety  to  danger  in  the  proper  manner,  the  engineer, 
observing  this  movement,  proceeds  at  full  speed.  A  train  should,  therefore,  be  protected 
by  hand  signal  whenever  it  enters  a  section,  unless  it  is  known  that  the  signal  indicates 
danger  behind  it. 

The  cost  of  erecting  these  signals,  with  the  necessary  apparatus  for  compressing  and 
conveying  the  air,  is  rather  high  as  compared  with  other  systems,  but  the  use  of  com- 
pressed air  in  place  of  manual  power  for  the  operation  of  switches  and  signals  in  yards, 
which  is  often  highly  advantageous,  affords  a  means  of  dividing  the  expense.  The  latest 
statistics  we  have  concerning  the  cost  of  maintenance  of  pneumatic  block  signals  are 
those  reported  for  the  ten  miles  on  the  Fitchburg  road  in  the  article  above  referred  to.  The 
cost  per  signal  per  yea.r  there  was  $133,  or  approximately  5u  per  cent,  more  than  that  of 
maintaining  clockwork  signals. 


THE    HALL    SIGNAL.* 

The  Hall  wire-circuit  automatic  block  signal  is  the  oldest  automatic  signal  used  to 
any  extent  in  this  country,  and  the  instruments  put  up  by  Mr.  Thomas  S.  Hall  on  16 
miles  of  the  Eastern  Eailroad  (now  the  Boston  &  Maine)  in  1871  are  still  in  use ;  but  the 
company  has  recently  been  reorganized,  after  several  years  of  inactivity,  and  the  signal, 
as  now  offered,  may  be  regarded  as  substantially  a  new  device,  the  improvements  over 
the  old  pattern  being  radical  in  many  respects.  The  apparatus  and  some  of  its  applica- 
tions were  described  in  the  Railroad  Gazette,  June  18,  September  12  and  December  5, 
1890.  The  signals  are  used  extensively  on  the  Hartford  Division  of  the  New  York,  New 
Haven  &  Hartford  and  on  the  Boston  &  Worcester  Division  of  the  Boston  &  Albany 
The  latter  road  in  1890  equipped  38  miles  of  double  track  with  continuous  blocks.  The 
New  York  Central  &  Hudson  River  has  recently  equipped  8£  miles  of  double  track  (de- 
scribed in  the  Railroad  Gazette,  December  5,  1890)  and  the  Michigan  Central  has  also  15 
miles  of  double  track  so  protected. 

The  Hall  Company  makes  no  use  of  the  track  circuit,  claiming  that  the  adjustment  of 
battery  and  of  instruments  is  such  a  delicate  operation  that  it  cannot  be  made  to  give 
satisfactory  service.  The  connection  from  one  signal  to  another  is  by  line  wire  upon 
poles,  and  passing  trains  actuate  the  signals  by  means  of  levers  placed  at  right  angles  to 
the  rails  in  such  a  position  that  the  wheels  depress  one  arm,  and,  by  the  elevation  of  the 
other,  open  or  close  an  electric  circuit.  The  signal  is  a  disc  of  very  light  weight,  in- 
closed within  a  wooden  case  in  which  is  a  circular  opening  covered  with  glass.  This  disc 
is  attached  to  the  armature  of  an  electromagnet  in  such  a  way  that  when  the  magnet  is 
energized  the  disc  is  held  up  out  of  sight,  and  on  the  cessation  of  the  current  falls  by 
gravity  in  front  of  the  glass  covered  opening.  It  is  colored  red,  and  the  surrounding 
surface  of  the  case  is  black,  so  that  when  visible  it  indicates  danger.  At  night  a  light 
is  placed  back  of  the  opening  Jn  the  case,  and  indicates  safety  or  danger  according 
as  the  disc  is  held  up  or  is  dropped,  the  disc  being  of  red  silk  and  translucent.  The 
signal  magnet  in  this  system  is  operated  ^directly  by  the  primary  circuit,  no  relay  or 
other  device  for  multiplying  power'  being  necessary.  The  current  whose  continuity 
is  necessary  to  maintain  the  signal,  at  "'all  clear"  is,  by  the  entrance  of  a  train  to  the 
section,  broken  at  two  places,  arid  one  of  these  contacts  is  so  broken  that  it  cannot  be 

--  Drawings  and  detailed  description  are  given  on  pages  53-58. 


THE  HALL  SIGNAL.  19 

restored  except  by  the   action  of  the   track   instrument  at  the  outgoing  end  of  the 
section. 

The  merits  claimed  for  the  Hall  signal  over  the  track-circuit  system  are  : 

All  operations  are  by  positive  making  and  breaking  of  metallic  connections. 
"  Shunts."  by  which  a  small  portion  of  a  current  still  flows  through  the  instrument  in- 
tended to  be  devitalized,  are  not  used.  With  this  apparatus  the  amount  of  battery 
power  may  be  variable  within  wide  limits,  and  extreme  delicacy  of  adjustment  of  magnet 
armatures  is  not  important.  The  number  of  electromagnets  is  reduced  to  a  minimum 
and  the  labor  of  care  and  inspection  is  correspondingly  less.  With  these  advantages, 
supplemented  by  good  design  and  workmanship,  the  number  of  unnecessary  stops  is 
claimed  to  be  largely  reduced.  In  fact,  the  company  shows  records  of  signals  which 
have  run  a  year  without  causing  a  single  unnecessary  stop.  It  is  claimed  that  such  a 
thing  as  showing  safety  while  danger  exists  has  never  been  known,  and  is,  in  fact, 
impossible. 

The  Hall  wire-circuit  system  does  not  indicate  the  presence  of  a  detached  car  in  the 
block  section.  The  company  admits  this  point,  but  claims  that  the  superior  reliability, 
with  reduced  cost  of  the  system,  is  of  enough  value  to  outweigh  it,  a-nd  also  that  the 
use  of  air  brakes  on  freight  trains,  and  the  exercise  of  good  discipline  otherwise,  practi- 
cally provide  for  such  a  contingency.  The  prices  charged  are  about  the  same  as  those 
asked  for  the  Union  clock-work  signals.  The  company  also  furnishes  a  combination 
of  track  instruments,  interlocking  instruments  and  relays  by  means  of  which,  when  two 
or  more  trains  enter  a  section  of,  say,  one  mile  in  length,  the  trains  being  a  half  mile 
apart,  each  train  will,  on  passing  a  track  instrument  2,000  feet  after  entering  the  section, 
break  the  circuit  controlling  the  signal  in  such  a  way  that  only  the  last  train  can  restore 
it  to  "all  clear  "  ;  in  other  words,  a  train  passing  out  of  a  section  cannot  clear  the  signal 
at  the  entrance  of  the  section  if  a  following  train  has  already  got  2,000  feet  within  it. 

The  cost  of  operation  of  the  Hall  signals  cannot  be  stated  with  accuracy,  because  the 
form  now  being  used  most  extensively  has  not  been  in  operation  long  enough  to  afford  a 
good  basis  for  estimating.  The  maintenance  of  a  number  of  the  signals  on  the  New 
York,  New  Haven  &  Hartford  has  cost  about  $65  per  year,  but  the  battery  power  of  the 
later  patterns  is  greatly  reduced,  and  the  cost  of  material  and  of  labor  is  correspond- 
ingly less. 


BLACK'S  MECHANICAL  BLOCK  SIGNAL.* 

This  apparatus  is  used  on  the  Manhattan  Elevated  (New  York  City)  and  other  pas- 
senger lines  in  the  vicinity  of  that  city.  The  Manhattan  has  a  series  of  32  continuous 
block  sections  in  operation.  The  instrument  consists  of  a  small  semaphore,  the  post 
being  cast  iron,  which  is  set  to  danger  by  a  lever  actuated  by  the  wheels  of  a  passing 
train.  The  same  signal  is  connected  by  a  gas-pipe  rod,  extending  along  the  road,  with 
another  track  instrument  at  the  outgoing  end  of  the  section,  and  the  train,  on  striking 
this,  resets  the  signal  at  safety.  The  maximum  length  of  block  operated  is  about  1,700 
ft.,  and  at  this  distance  the  signals  have  worked  with  great  success  for  two  or  three  years. 
It  will  be  understood  that  the  moderate  speed  and  uniform  length  of  the  trains  on  these 
city  railroads  permit  the  use  of  a  signal  whose  capabilities  for  longer  blocks  or  for  more 
varied  service  are  limited. 

SUMMARY. 

To  briefly  summarize  the  salient  features  of  the  different  systems  of  block  signaling, 
it  may  be  said  that  the  simplest  form,  that  which  we  have  termed  "single-track  block- 
ing," and  which  is  used  on  various  Western  roads,  is  cheap,  readily  adapted  to  nearly 
all  roads  of  light  traffic  and  generally  to  a  road  of  any  traffic,  and  is  an  absolute  necessity 
to  any  road  which  would  avoid  the  well-known  difficulties  connected  with  protecting 
trains  from  rear  collisions  by  flags,  lamps  and  torpedoes.  The  drawbacks  to  the  use  of 
this  system  are  the  liability  of  officers  and  trainmen  to  expect  more  of  it  than  it  can,  in 
the  nature  of  things,  perform.  Where  there  is  only  one  signal  at  a  station,  while  there 
may  be  two  or  a  half  dozen  switches,  and  where  the  distance  between  stations  is  so  long 
that  trains  must  sometimes  be  allowed  to  follow  each  other  within  the  same  block,  the 
block  system  is  not  responsible  for  and  cannot  be  charged  with  the  various  dangerous 
contingencies  that  may  arise.  In  fact,  the  system  can  in  such  cases  be  used  only  a  part 
of  the  time.  The  danger  is  that  when  or  where  it  is  not  in  use  the  men  are  liable  to 
assume,  perhaps  unconsciously,  that  it  is  in  use,  instead  of  adopting  other  precautions 
such  as  would  be  taken  had  the  block  system  never  been  heard  of. 

The  block  system  in  use  on  the  Pennsylvania  is  simply  a  more  careful  and  system- 
atic application  of  this  same  principle.  The  only  reason  why  scores  of  roads  do  not 
imitate  the  Pennsylvania  seems  to  be  simply  a  lack  of  the  courage  requisite  to  incur  a 
considerable  expenditure  for  first  cost,  and  a  failure  to  appreciate  the  fact  that  short 

*  Drawings  and  detailed  description  are  given  on  page  62. 


BLACK  S  MECHANICAL  BLOCK  SIGNAL.  21 

sections  are  not  essential  to  the  utility  of  the  system.  Officers  too  readily  assume  that  a 
large  expenditure  for  operators  (to  give  their  exclusive  attention  to  block  signaling)  is 
indispensable,  whereas  the  system  in  many  cases  could.be  advantageously  adopted  with- 
out going  to  that  expense. 

The  Sykes  system  is  admitted  by  the  best  judges  among  those  who  have  used  it  to 
be  valuable,  but  its  cost  both  for  introduction  and  maintenance  is  rather  high.  Its  use 
is  still  limited  to  the  busiest  lines,  even  in  England.  Its  value  is  largely  or  wholly 
neutralized  if  permissive  blocking  is  practiced,  and  very  few  roads  have  progressed  to 
the  point  where  they  wholly  forbid  that  practice. 

The  special  merit  of  automatic  signals  lies  in  the  possibility  of  reducing  the  run- 
ning expenses  90  per  cent.,  more  or  less,  below  the  cost  of  a  man-operated  system.  As- 
suming that  such  imperfections  as  they  are  now  burdened  with  can  be  eliminated,  and 
especially  that  they  can  be  made  perfectly  self -detecting,  the  question  concerning  their 
general  availability  is,  will  the  unnecessary  stops  caused  by  the  failure  of  apparatus  and 
extraneous  accidents  delay  traffic  to  such  an  extent  as  to  compel  a  resort  to  the  regular 
block  system  (with  operators  at  each  station)  ?  Some  English  experts  claim  that  this 
will  be  the  ultimate  outcome.  It  is  to  be  remembered,  however,  that  they  judge  largely 
by  experience  on  the  most  crowded  lines,  and  that  by  reason  of  the  low  rates  of  wages  in 
that  country  the  question  of  operating  expense  does  not  assume  the  importance  that  at- 
taches to  it  here.  Granting  this  point,  it  still  remains  true  that  many  hundred  miles  of 
road  in  this  country  now  carry  a  volume  of  traffic  sufficiently  large  to  demand  a  block 
system  of  some  sort,  while,  at  the  same  time,  they  will  not  for  many  years  be  used  by  a 
sufficient  number  of  trains  to  make  five-minute  delays  intolerable. 

It  may  therefore  be  said  that  there  are  three  classes  of  roads  in  this  country  which 
afford  fields  for  three  different  kinds  of  block  signaling  respectively  : 

1.  Those  parts  of  large  roads  which  lie  in  the  vicinity  of  the  principal  cities,  where 
yards  are  located  very  close  together,  and  where  the  traffic  is  very  heavy — these  need 
man-operated  signals,  with  short  blocks. 

2.  Many  double-track  roads  of  less  importance  need  the  block  system,  but  cannot 
afford  to  establish  stations  as  close  together  as  is  necessary  to  run  trains  at  short  in- 
tervals.    This  is  the  field  for  automatic  signals. 

3.  The  roads  of  thin  traffic  and  with  long  stretches  between  stations  cannot  afford 
special  block  operators,  and  cannot  afford  even  the  few  hundred  dollars  per  block  neces- 
sary to  establish  an  automatic  system.    These  should  block  by  means  of  their  regular 
station  operators.    This  is  especially  true  of  roads  where,  by  reason  of  heavy  grades, 
prevalence  of  fogs,  or  other  conditions,  the  speed  of  trains  cannot  be  maintained  at  a 
reasonably  uniform  rate,  and  of  those  located  in  northern  climates  where  flagging  in 
winter  is  dangerous  both  to  the  men  and  the  trains. 


APPENDIX. 


THE    SYKES   BLOCK-SIGNAL    APPARATUS. 

[October  3,  1890.] 

What  is  known  as  the  "  Sykes  System"  is  the  application  to  an  ordinary  manual 
block  system  of  certain  electrical  and  mechanical  devices  which  insure  that  the  signal 
governing  the  entrance  to  a  given  block  cannot  be  cleared  until  the  preceding  train  has 
passed  out  of  it  and  the  operator  at  the  end  of  the  block  has  given  his  consent. 

Under  the  practice  of  The  Union  Switch  &  Signal  Co.,  which  has  proprietary  control 
of  the  Sykes  system  for  this  country,  these  results  are  secured  by  the  use  of  a  Sykes  lock 
instrument,  an  interlocking  relay,  and  a  short*  insulated  section  of  track,  with  proper 
metallic  circuits  connecting  these ;  also  a  bell  wire  or  telegraph  line  for  communicat- 
ing between  adjacent  block  stations. 

The  Sykes  lock  instrument  is  placed  in  the  operator's  office  immediately  over  the 
lever  by  which  he  controls  his  signal.  The  interlocking  relay  is  located  in  any  conven- 
ient place,  usually  in  a  closet.  The  insulated  section  of  track  is  located  at  the  entrance 
of  the  block,  and  is  usually  two  rails  in  length  (about  60  ft.).  The  bell- wire  push-but- 
'tons  are  placed  near  the  signal  lever  and  the  Sykes  instrument. 

The  connection  and  relative  operation  of  the  signal  lever  and  the  Sykes  lock  instru- 
ment are  illustrated  by  Figs.  1  and  2,  which  show  two  operating  levers  and  two  lock  in- 
struments, the  regular  equipment  of  a  block  station  working  blocks  in  both  directions. 

The  important  connections  are  the  lock  bolt,  the  lock  bar,  the  lock  rod,  and  the 
plunger  rod.  Normally,  the  signal  lever  being  home  and  the  signal  at  danger,  the  lock 
bolt  is  entered  in  a  hole  in  the  lock  bar,  and  both  plunger  rod  and  lock  rod  are  in  their 
extreme  upward  positions,  displaying  the  words  "Clear"  and  "Locked"  (Fig.  1),  which 
indicate  to  the  operator  that  the  plunger  is  free  to  be  worked  (and  thus  unlock  a  signal 
lever  at  an  adjacent  block  station),  but  that  his  own  signal  lever  is  locked  and  cannot  be 
moved. 

The  operation  in  practice  is  as  follows,  everything  being  normal — levers  home,  signals 
at  danger,  and  tracks  unoccupied :  If  the  operator  desires  to  allow  a  train  to  enter  one  of 


THE  SYKES  BLOCK-SIGNAL  APPARATUS. 


Fig.  1.  Levers  and  Lock.  F  g.  2. 


24  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

the  blocks  which  his  signals  control,  he  notifies  the  operator  next  in  advance  (by  bell 
wire  or  telegraph  line);  the  advance  operator,  if  everything  is  all  right,  responds  by 
u  plunging"  on  one  of  his  instruments.  That  has  the  effect  of  releasing  the  lock  rod  at 
the  first  station;  the  lock  rod  falls  by  its  own  weight,  and  in  so  doing  withdraws  the 
lock  bolt  from  the  lock  bar.  The  operator  then  pulls  over  his  lever  and  clears  his  signal; 
this  movement  forces  the  lock  bar  forward,  and,  through  the  action  of  the  inclined  plane 
and  roller,  also  forces  the  lock  rod  upward  to  its  normal  position,  where  it  is  automatically 
held  until  again  released  by  the  operator  at  the  station  in  advance.  This  upward  move- 
ment of  the  lock  rod  leaves  the  lock  bolt  free  to  be  sprung  into  the  hole  in  the  lock  bar, 
when  the  lever  is  again  returned  to  its  normal  position. 

The  only  function  of  the  Sykes  system  so  far  alluded  to  is  that  by  which  the  operator, 
on  request  of  an  adjacent  operator,  may  "plunge"  and  thus  release  the  latter' s  signal 
lever.  The  additional  and  important  function  of  the  combined  apparatus  is  to  prevent  an 
operator  from  plunging  a  second  time  until  the  train  for  which  the  preceding  operator 
desired  to  clear  his  signal  has  passed  into,  through,  and  out  of  the  block  in  question. 
This  result  is  secured  by  the  combined  action  of  the  Sykes  instrument,  the  interlocking 
relay,  and  the  insulated  section  of  track. 

The  Sykes  instrument  is  shown  in  position  and  in  connection  with  the  operating 
signal  levers  in  Figs.  1  and  2,  as  above  referred  to.  It  is  shown  in  detail  in  Figs.  3,  4,  5, 
6  and  7. 

Fig.  3  exposes  those  parts  which  are  employed  in  unlocking  the  signal  lever.  When 
an  adjacent  operator  plunges  he  simply  passes  a  current  through  the  electromagnets  21 
of  his  neighbor's  instrument,  thus  attracting  and  raising  armature  22,  and  imparting  a 
slight  rotation  to  balanced  lever  23  about  its  centre  24.  This  releases  trip  25  (which  then 
is  free  to  rotate  about  its  centre  26)  and  permits  the  lock  rod  35  to  drop  by  its  own  weight, 
and  thus  unlock  the  operator's  signal  lever  as  explained  in  connection  with  fig.  2. 

Fig.  5  best  illustrates  the  action  and  results  of  plunging.  When  plunger  27  is  push- 
ed in,  cross-bar  28  (figs.  6  and  6)  is  raised,  breaking  one  circuit  and  completing  another 
by  means  of  springs  at  29  (figs.  3  and  6).  When  plunger  27  is  forced  out  to  its  original 
position  by  the  action  of  spring  30,  an  electrical  contact  is  effected,  by  springs,  at  31 
(figs.  5  and  6).  One  end  of  cross-bar  28  is  free  to  rotate,  in  one  direction  only,  about  90 
degrees,  but  is  restored  to  its  original  position  by  a  small  contained  spiral  spring  ;  thus, 
in  fig.  5,  the  small  projection  on  left  of  cross-bar  28  causes  it  to  revolve  on  the  upward 
stjoke,  and  no  contact  at  31  is  effected.  But  on  the  downward  stroke  the  same  projection 
presses  the  flat  springs  to  the  left  and  effects  the  desired  contact.  In  order  that  this  con- 
tact may  not  be  too  brief  (an  electromagnet  at  adjacent  station  is  thereby  charged)  the 
downward  stroke  of  cross-bar  28  is  retarded  by  dash  pot  32,  which  has  a  small  vent  hole 
below. 

In  plunging  there  is  also  an  important  mechanical  interaction  between  plunger  rod  33 


THE  SYKES  BLOCK-SIGNAL  APPARATUS. 


BLOCKED 


--:®i 

fclJ 


1' 


- 


I 


Fig.  4. 


\ 


±1 


Fig.  6— Section  on  A  B.          SYKES  SYSTEM— DETAILS.  Fig  7— Section  on  E  F. 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 


and  trip  rod  34  (figs.  4,  5  and  7).  Plunger  rod  33  has  attached  to  it  a  pin  3o  (figs.  4  and 
5.  Plunger  27  has  attached  to  it  a  side  piece  37  (figs.  4,  5  and  7).  Trip  rod  34  has  attached 
to  it  a  pawl  piece  38  and  a  sliding  block  89  (figs.  4,  5  and  7).  Normally,  as  shown  in 
fig.  2,  the  plunger  rod  is  in  its  extreme  upper  position.  In  this  position,  as  shown  in 
fig.  5,  the  plunger  rod  33,  by  means  of  pin  36,  supports  pawl  piece  38  and  the  trip  rod 
34,  thus  displaying  the  word  "Clear"  (fig.  4)  to  the  operator,  which  signifies  that  his 
plunger  is  free  or  clear,  and  may  be  operated  in  response  to  request  from  adjacent  oper- 
ator. 

When  the  plunger  27  is  pushed  in,  the  side  piece  37  forces  pawl  piece  33  off  from 
pin  36,  and  trip  rod  34  drops ;  at  the  same  time  sliding  block  39,  previously  sup- 
ported by  the  pressure  of  pawl  piece  38,  drops  until  it  rests  on  side  piece  37,  which  is 
tnen  under  it.  When  the  plunger  comes  out,  on  its  return  stroke,  sliding  block  39  falls 
still  farther  on  to  the  extension  or  foot  of  side  piece  37,  preventing  the  plunger  27  from 

being  again  forced  in.  When  the  trip  rod  34 
dropped  the  word  "Blocked"  was  displayed 
instead  of  the  word  "Clear,"  signifying  to  the 
operator  that  he  could  not  plunge  again 
until  certain  conditions  had  been  complied 
with.  To  release  the  plunger,  the  trip  rod  must 
be  lifted  back  to  its  normal  position.  This  can 
be  effected  only  by  reversing  the  operator's 
signal  lever  and  again  putting  it  in  the  for- 
ward or  home  position.  When  the  signal  lever 
is  reversed,  the  plunger  rod  is  drawn  to  the 
bottom  of  its  stroke  (see  fig.  2).  In  its  down- 
ward stroke  the  pin  36  on  plunger  rod  33  (figs. 
4  and  5)  forces  aside  pawl  piece  38,  which 
then  snaps  back  in  normal  position  above  pin 
36,  resting  on  and  supported  by  it.  When 
the  signal  lever  is  returned  to  its  normal  or 
home  position,  and  the  plunger  rod  is  forced 
upward,  it  lifts  with  it  trip  rod  34  and  restores 
Fig.  5 -Section  on  L  N.  it  to  iis  normal  position  ;  the  pressure  of 

pawl  pieces  38  against  sliding  block  39  keeps  them  in  the  same  relative  position  as  when 
the  trip  rod  was  down,  and  in  this  way  the  sliding  block  39  is  lifted  up  out  of  the  way 
and  the  plunger  is  ready  to  be  operated  again,  as  is  indicated  by  the  word  "  Clear,"  which 
is  again  displayed.  It  thus  appears  that  when  an  operator  plunges  he  is  mechanically 
prevented  from  plunging  a  second  time  until  he  reverses  his  lever  and  again  restores  it  to 
its  normal  or  home  position. 


THE  SYKES  BLOCK-SIGNAL  APPARATUS. 


27 


It  will  no  v  be  shown  that  when  an  operator  plunges  and  releases  the  lever  of  the 
operator  next  to  the  rear,  the  electrical  circuit  thus  utilized  is  automatically  broken,  and 
cannot  be  made  complete  again  until  the  train  for  which  the  preceding  operator 
desired  to  give  a  clear  signal  has  passed  over  the  intervening  block.  The  automatic  action 


Fig.  8. 


Fig.  9. 


Arrangement  of  Circuits. 
NOTE.— 50  is  the  lock-wire  ;  the  wire  below  is  the  common  return  for  lock  and  bell  circuits. 

THE    SYKES   SYSTEM. 

of  breaking  and  restoring  the  lock  circuit  may  be  understood  by  reference  to  figs.  8  and 
9,  which  indicate  the  relation,  connection  and  mutual  interaction  of  the  Sykes  instrument, 
the  interlocking  relay  and  the  insulated  section  of  track.  Two  tracks  are  shown  in  the 
plan,  but  only  such  instruments  and  circuits  are  shown  as  are  necessary  for  the  control  of 
trains  in  both  directions,  between  two  adjacent  block  stations  8  and  9  For  a  continuous 
system  two  sets  of  instruments  at  each  station  are  required.  Two  different  views  of  the 
top  of  the  Sykes  instrument  are  given  in  each,  fig.  8  and  fig.  9,  so  as  to  better  display  the 
contacts  and  circuits  which  are  broken  and  established  by  the  up  stroke  and  the  down 


28  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

stroke  of  the  cross-bar  28  which  takes  its  motion  from  the  plunger  27,  as  has  been  pre- 
viously explained.  The  interlocking  relays  are  shown  in  their  normal  condition,  the  upper 
magnets  dead  (owing  to  the  break  in  the  circuit  at  31),  and  their  armatures  down  ;  the 
lower  magnets  charged  from  the  track  battery,  and  their  armatures  up. 

Suppose  operator  8  desires  to  clear  his  signal  to  allow  a  train  to  pass  8  towards  9;  he 
uses  his  bell  wire  or  Morse  instrument  to  request  operator  9  to  release  his  lever.  If  the 
road  is  clear  and  everything  normal,  operator  9  responds  by  plunging;  this  forces  cross- 
bar 28  upward,  and  the  spring  30,  restrained  by  the  dash  pot,  slowly  forces  it  down 
again.  Kef  erring  to  fig.  9,  the  upward  stroke  of  cross-bar  28  (lower  view)  breaks  the 
contact  between  spring  29  and  the  right-hand  contact  screw,  and  effects  a  contact  be- 
tween spring  29  and  the  left-hand  contact  screw;  this  completes  circuit  29,  40,  41,  66,  42, 
62,  43,  44,  45,  46,  47,  29,  48,  49,  50,  61,  and  charges  the  electromagnets  at  station  8,  re- 
leasing the  operator's  lever  at  that  point  and  permitting  him  to  clear  his  signal  for  the 
entrance  of  the  train  into  the  block,  which  extends  from  station  8  to  station  9.  The 
action  of  tripping  the  lock  rod  is  instantaneous,  and  requires  only  a  momentary  charging 
of  the  electromagnets.  Referring  to  the  upper  view  in  fig.  9,  it  is  understood  that  that 
end  of  cross-bar  28  rotates  during  the  upward  stroke,  and  effects  the  contact  31  only  on 
its  downward  stroke  ;  this  contact  31  has  the  effect  of  breaking  the  circuit  previously 
established.  Contact  31  completes  circuit  31,  52,  54,  53  ;  electromagnet  54  thus  charged 
attracts  its  armature,  which  is  automatically  hooked  up  by  the  spring  hook  on  leg  of 
armature  of  electromagnet  55  ;  this  breaks  the  original  circuit  at  56,  and  operator  9  can- 
not again  unlock  a  lever  for  operator  8  until  the  train  has  passed  over,  and  off  of,  the  in- 
sulated section  of  track  57,  58.  When  no  train  is  on  the  insulated  section,  circuit  59,  57, 
61,  55,  60,  58  is  complete,  electromagnet  55  is  charged,  its  armature  held  up  and  con- 
tact 62  kept  good.  When  a  train  passes  over  insulated  section  57,  58,  the  first  axle 
establishes  a  short  circuit  with  battery  59  and  devitalizes  electromagnet  55  ;  its  armature 
drops,  destroying  contact  62,  but  allowing  armature  54  to  drop  also,  thus  restoring  con- 
tact 56,  which  was  previously  broken.  Contact  62  cannot  be  restored,  however,  as  long 
as  the  short  circuit  at  the  insulated  section  of  track  exists.  Each  axle  of  the  train  is  a 
possible  short-circuit  path,  so  that  the  entire  train  must  have  passed  over  and  off  the  in- 
sulated section  before  the  short-circuiting  ceases  ;  then  the  original  circuit  59,  57,  61,  55, 
60,  58  is  re-established,  electromagnet  55  is  charged,  its  armature  attracted,  and  contact 
62  restored  and  maintained ;  and  the  original  lock  circuit  by  which  operator  9  plunged 
and  released  a  lever  in  station  8  is  again  made  complete.  Operator  9  had  to  reverse  his 
signal  lever  in  order  to  admit  the  train  to  the  insulated  section  of  track,  and  in  putting 
his  lever  home  or  into  its  normal  position  he  unlocked  his  own  plunger,  so  he  could  again 
plunge  for  8.  If  the  train  had  passed  completely  over  the  insulated  section  of  track,  the 
lock  circuit  would  have  been  restored  and  his  plunging  for  8  would  be  effective,  and  he 
would  release  his  lever  for  another  train. 


THE  SYKES  BLOCK-SIGNAL  APPARATUS.  29 

In  the  case  of  the  first  block  station  in  a  series  it  is  necessary  to  introduce  some  de- 
vice by  which  each  train  entering  that  block  under  a  clear  signal  will  automatically  set 
that  signal  to  danger  again.  This  is  accomplished  by  the  use  of  what  is  known  as  an 
"  electric  slot "  in  the  connections  between  the  operator's  lever  and  the  signal  blade. 
This  electric  slot  involves  an  electromagnet  normally  charged  and  taking  current  from 
a  battery  through  the  two  rails  of  an  insulated  section  of  track :  when  the  current  is 
passing  through  the  electromagnet  the  connection  between  the  operating  lever  and  the 
signal  blade  is  preserved  complete,  and  the  operator  has  full  control  over  his  signal. 
When  a  train  reaches  the  insulated  section  of  track,  however,  the  first  and  all  other 
axles  establish  a  short  circuit ;  the  electromagnet  is  thus  discharged,  the  connection 
broken  and  the  signal  set  to  danger  by  the  action  of  its  counter- weight.  The  operator 
cannot  again  get  control  of  his  signal  except  by  putting  his  signal  lever  normal ;  when 
that  has  been  done  and  the  circuit  restored  by  the  complete  passage  of  the  train,  the  con- 
nection between  lever  and  signal  blade  is  automatically  restored  and  the  operator  again 
has  control  of  his  lever,  subject,  of  course,  to  the  action  of  the  operator  next  in  advance, 
who  may  plunge  and  unlock  him  if  all  the  conditions  are  favorable. 

It  has  been  shown  :  First,  that  an  operator  by  plunging  may  unlock  the  signal  lever 
of  the  preceding  operator.  Second,  that  in  so  doing  his  plunger  is  automatically  locked 
up,  and  can  be  unlocked  only  by  reversing  his  lever  and  putting  it  home  again  (in  other 
words,  giving  a  clear  signal  and  then  the  danger  signal).  Third,  that  the  lock  circuit 
utilized  by  the  inward  stroke  of  the  plunger  is  automatically  broken  during  the  outward 
stroke  of  the  plunger,  and  can  be  restored  and  made  complete  only  by  the  passage  of  the 
train  onto,  over  and  off  of  the  insulated  section  of  track. 

The  resultant  effect  of  the  combined  apparatus  under  these  several  conditions  insures 
that  "the  signal  governing  the  entrance  to  a  given  block  cannot  be  cleared  until  the  last 
train  which  received  a  clear  signal  to  enter  that  block  has  passed  oat  of  it,  and  the 
operator  at  the  end  of  the  block  has  given  his  consent." 


AUTOMATIC  SIGNALS  ON  THE  BOSTON  &  ALBANY. 

[June  24, 1887.    Written  by  G.  W.  Blodgett.] 

This  road  has  had  a  larger  experience  with  electric  signals  than  almost  any  other  in 
the  country.  A  large  portion  of  the  road  is  now  equipped  with  such  signals,  and  addi- 
tions to  the  plant  are  constantly  being  made.  A  brief  description  of  the  apparatus  em- 
ployed will  be  followed  by  some  account  of  its  practical  working  and  the  results  obtained. 

The  road  has  double  track  throughout  its  whole  length,  except  the  first  ten  miles, 
where  there  are  four  tracks.  This  short  distance  and  some  other  detached  portions  of 
the  road  have  continuous  overlapping  blocks.  The  remaining  applications  (with  a  single 
exception)  are  "station  blocks"  so  called;  that  is,  there  is  a  signal  each  side  of  the 
station  about  one-half  mile  distant,  which  is  connected  with  every  switch  in  the  track  to 
which  the  signal  belongs,  and  the  function  of  which  is  to  protect  a  train  while  standing 
at  a  station  or  switching.  As  traffic  increases,  or  for  other  reasons  it  becomes  advisable 
so  to  do,  these  applications  can  be  made  parts  of  a  system  of  continuous  blocks  with  no 
other  change  than  simply  overlapping  the  sections. 

For  the  first  mile  from  Boston  all  trains  are  of  the  same  class  and  run  on  the  same 
tracks.  After  that  they  diverge,  express  passenger  and  freight  trains  running  westward 
on  track  No.  1  and  eastward  on  track  No.  2,  while  suburban  passenger  trains  travel 
westward  on  track  No.  3  and  eastward  on  No.  4  for  10  miles,  to  the  end  of  the  four-track 
section.  A  large  part  of  the  suburban  trains  go  no  farther,  and  beyond  this  point  all 
trains  again  run  on  two  tracks. 

In  the  first  mile  the  signals  are  about  -fc  mile  apart,  then  %  mile  for  two  miles  more 
(which  includes  a  large  yard  for  outgoing  and  another  for  incoming  freight  trains,  be- 
sides two  important  junctions),  and  then  about  a  mile  apart  as  far  as  the  continuous 
blocks  extend. 

•  The  larger  part  of  the  road  is  equipped  with  the  rail  circuit  clockwork  signals  of  the 
Union  Switch  and  Signal  Co.  The  first  applications  of  this  signal  were  made  in  l8b2, 
when  6  blocks  were  put  up  as  an  experiment. 

BLOCK   SIGNALS  WITH   BAIL    CIRCUITS. 

The  road  is  divided  into  sections  of  varying  lengths  according  to  the  amount  of  traffic 
or  local  circumstances,  as  above  mentioned,  each  of  which  sections  has  a  signal  at  the 


AUTOMATIC  SIGNALS  ON  THE  BOSTON  &  ALBANY. 


31 


ntrol/ing  Si&ial. 


*  '^j~  t  '   "  - .- 

ytSS^ginning  (operated  by  clockwork  and  a 

position  indicat- 
train  enters  the  sec- 
poijn,,  and  restored  to  that 
the  train  leaves  the 

section.  Each  section  is  electrically  in- 
sulated from  those  before  and  behind  it. 
At  the  end  farthest  from  the  signal  is  an 
electric  battery  giving  a  constant  current, 
which  is  connected  to  the  track,  one  pole 
to  each  rail ;  at  the  signal  end  of  the  sec- 
tion the  coils  of  a  relay  are  connected  to 
the  rails  in  like  manner,  so  that  there  is  a- 
constant  flow  of  electricity  from  the  battery 
through  one  line  of  rails  to  the  relay, 
thence  through  its  coils  to  the  other  line  of 
rails,  thence  by  these  rails  back  to  the  bat- 
tery. This  relay  controls  the  local  circuit 
(so  called)  of  another  battery  connected  to 
an  electromagnet  in  the  signal,  which 
governs  the  motion  of  the  clockwork 
operating  it. 

Fig.  1  shows  the  track  clear,  relay  It 
holding  the  local  circuit  through  8  closed. 

The  successful  operation  of  signals  by 
means  of  rail  circuits  requires  that  the 
electromotive  force  (or  pressure,  as  it  may 
be  considered)  of  the  battery  connected  to 
the  rail  shall  be  so  small  that  there  will  be 
only  slight  leakage  from  the  rails  even  in 
wet  weather.  It  is  found  advisable,  there- 
fore, to  include  in  the  track  circui  only  the 
coils  of  a  relay  of  low  resistance,  and  make 
this  relay  open  and  close  the  circuit  for 
another  battery  of  any  size  desired,  which 
shall  operate  the  signal  mechanism.  There 
are  then  two  electric  circuits  for  each 
signal ;  one  through  the  rails  control- 
ling another  through  the  signal.  Both 


32 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 


circuits  are  normally  closed  ;  that  is,  there  is  a  constant  flow  of  electricity  through  the 
whole  length  of  each.  The  clockwork  is  so  constructed  that  when  the  current  is  passing 
through  the  magnet  the  signal  is  held  in  the  position  of  "all  clear"  or  "safety."  When 
this  is  interrupted,  the  signal  makes  one-fourth  of  a  revolution  to  the  position  indicating 
"danger"  or  "stop."  ' 

When  a  train  enters  the  section  the  current  in  the  rails  takes  the  path  of  least  resist. 
ance,  through  the  wheels  of  the  train  instead  of  the  relay  magnet.  The  armature  of  this 
magnet  then  falls  off  and  opens  the  circuit  of  the  battery  controlling  the  signal,  and  this 
takes  the  "  danger"  position  as  Jong  as  the  section  is  occupied.  When  the  rear  of  the 
train  passes  out  of  the  section  the  circuits  are  again  closed  and  the  signal  shows  clear  ; 
but  if  so  much  as  a  pair  of  wheels  remains  in  any  portion  of  the  section  the  signal  will 
continue  to  show  danger  until  the  obstruction  is  removed.  The  same  effect  is  produced 
whenever,  for  any  cause,  either  circuit  is  interrupted  —  if,  for  instance,  the  battery  fails, 


iMile 


Signal  S  'goes  to  Danger  at  A         Signal  Szgoes  fo  Danger  afC. 

u     n      n     U"AH clear" „  D  °  //      a      //    //  "A II  clear  >,  £/>dofnext 


over/ap. 


or  the  wires  are  broken,  or  the  clockwork  is  run  down,  the  signal  shows  "  danger."  If  a 
rail  in  the  track  is  broken,  and  the  parts  separated  by  so  much  as  ^o  of  an  inch,  the 
signal  will  be  at  danger.  Many  instances  of  this  kind  have  occurred,  and  not  a  few  where 
the  indications  was  most  timely.  Indeed,  the  use  of  automatic  signals  has  often  dis- 
covered broken  rails  which  might  have  remained  in  the  track  a  long  time  without  such 
displacement  of  parts  as  would  have  rendered  them  liable  to  detection  by  the  ordinary 
methods  of  inspection. 

To  make  perfect  electrical  connection  between  the  rails,  a  wire  extends  past  each 
joint,  the  ends  of  which  are  connected  to  the  two  rails  by  a  tight-fitting  pin  in  a  hole 
drilled  in  the  flange  of  the  rail.  While  rails  are  new  and  fish-plates  tightly  screwed  up, 
this  is  not  absolutely  needed,  but  as  soon  as  they  begin  to  rust  there  is  trouble  if  the 
rails  be  not  connected  by  the  wires.  Signals  have  worked  for  several  months  with  an 


AUTOMATIC  SIGNALS  ON  THE  BOSTON  &  ALBANY.  33 

unwired  track,  but  ordinarily  they  will  do  so  only  for  a  few  weeks,  even  if  rails  and  fish- 
plates be  perfectly  new. 

Figs.  2  and  3  show  the  circuit  breakers  connected  with  each  switch,  and  the  wire  con- 
nections by  which  the  rails  of  side  tracks  are  included  in  the  track  circuit,  for  the  pur- 
pose of  keeping  signals  at  "danger"  until  trains  entering  the  side  track  are  fully  clear  of 
the  main  line.  In  fig.  3  points  X and  Fare  connected  by  the  curved  flat  brass  which  is 
held  against  them  by  a  spring,  and  the  two  rails  are  thus  electrically  connected,  the  same 
as  when  a  pair  of  wheels  is  upon  them.  In  fig.  2  the  switch  rail  T  having  been  with- 
drawn from  the  main- track  rail,  has  pushed  the  brass  connections  away  from  X  and  J, 
breaking  the  connection  between  the  opposite  rails.* 

When  the  block  signals  are  continuous— that  is,  with  no  spaces  between  the  sections — 
the  safety  of  trains  folio  wing  each  other  at  short  intervals  is  very  greatly  increased  by 
making  the  sections  overlap  each  other.  This  causes  a  signal  to  remain  at  danger  until 
the  train  has  passed  a  certain  distance  (usually  about  1,000  ft.)  beyond  the  next  signal. 
While  the  train  is  running  this  short  distance  there  are  two  red  signals  behind  it,  one  at 
the  beginning  of  the  section  where  the  train  is,  and  the  other  at  the  beginning  of  the  pre- 
ceding section. 

The  arrangement  of  circuits  which  accomplishes  this  is  shown  in  fig.  4,  which 
assumes  the  block  to  be  one  mile  in  length.  The  principal  track  circuit  for  the  signal 
S1  passes  through  the  armature  of  a  relay,  J?1;  the  coils  of  this  relay  are  in  a  wire  circuit 
connected  with  the  battery  J52,  which  is  controlled  by  a  relay,  -S2,  placed  at  the  end  of  the 
overlap.  The  coils  of  this  last  relay  are  connected  to  the  rails  of  the  overlap.  It  will 
be  seen  that  a  train  on  any  portion  of  this  short  section  will  operate  the  relay  Rz  and 
consequently  -S1,  and  set  both  signals.  Hence,  so  long  as  an  engineman  does  not  pass  a 
red  signal  he  can  never  approach  a  preceding  train  nearer  than  the  length  of  the  overlap. f 

Signals  are  placed  a  short  distance  (usually  about  200  ft.)  beyond  the  beginning  of 
the  section,  in  Border  that  an  engineer  may  see  the  signal  operate  for  his  train.  Should 
it  fail  to  do  so,  he  is  to  stop,  the  same  as  for  a  danger  signal,  and  proceed  only  as  the 
way  is  known  to  be  clear.  The  engineer  of  every  train  stopped  by  a  signal  must  with- 
out delay  report  the  stop  and  the  cause  if  known  (on  blank  cards  provided  for  the  pur- 
pose) as,  for  instance,  a  preceding  train  in  section  or  an  open  switch.  If  the  cause  be 
not  apparent  to  the  engineer,  he  simply  reports  "  cause  not  known,"  and  it  is  put  in  the 
hands  of  a  repairman  to  investigate.  When  the  latter  has  ascertained  the  cause  (for 
instance,  a  broken  rail,  failure  of  battery,  derangement  of  some  part  of  the  apparatus  or 
other  cause  not  at  first  apparent)  he  returns  the  card  with  his  explanation  indorsed 

*  In  figs.  2  and  3,  B  is  the  battery  at  one  end  of  the  block  section,  and  B  €he  relay  controlling  the  signal  at  the 
other  end.  The  switch  S  (or  any  number  of  switches)  may  be  at  any  point  between  these  two. 

t  When  a  train  is  on  the  section  C  D  relay  722  is  demagnetized,  thus  opening  both  the  circuits  through  battery 
jB2 ;  S2  and  S1  then  both  show  "  danger.'1  When  a  train  is  in  the  section  beyond  D,  relay  B3  is  demagnetized,  hold- 
ing S'2  to  "  danger."  Signal  S*  stands  200  ft.  from  C  and  800  ft.  from  D. 


34  AMERICAN  PRACTICE  IX  BLOCK  SIGNALING. 

thereon.  If  lie  cannot  find  out  the  cause,  he  returns  the  card  with  that  statement,  and 
it  is  usually  never  ascertained.  There  is  a  small  fraction  of  one  per  cent,  of  such  stops 
at  signals.  Jt  is  quite  certain  that  some  of  these  are,  due  to  previous  trains,  open 
switches  or  other  legitimate  causes,  but  in  the  absence  of  positive  proof  they  are  not  so 
classified.  Sometimes  employes  needlessly  cause  stops  of  trains  at  signals,  and  to  save 
themselves  the  consequences  carefully  conceal  the  fact,  which  is  not  always  afterwards 
discovered,  and  when  this  is  the  case  such  stops  have  to  be  reported  "  cause  unknown." 
A  careful  record  is  kept  of  all  stops  and  their  causes,  and  every  month  a  debit  and  credit 
account  is  made  up  of  the  operation  of  the  signals  on  each  division  of  the  road,  which 
shows  at  a  glance  what  proportion  of  stops  is  due  to  neglect  of  employes,  defective 
apparatus,  unavoidable  causes,  etc.,  as  well  as  all  legitimate  stops. 

The  only  stops  credited  to  the  system  are  those  due  to  (1)  previous  trains  in  section, 

(2)  open  switches,  (3)  broken  rails,  (4)  repairing  track,    (5)   [sometimes]  using  single 
track,  (6)  cars  left  on  turnouts  too  near  the  main  track.   Lost  motion  in  switches,  broken 
track  wires,  Of  any  other  failure  of  the  track  circuit  is  usually  charged  to  the  neglect  of 
trackmen ;  those  due  to  failure  of  batteries,  corrosion  of  apparatus,  and  certain  other 
derangements  to  neglect  of  signalmen,  so  that  the  blame  may  be  placed  where  it  belongs. 
Employes  are  held  to  a  strict  account  for  all  avoidable  stops  caused  by  them,  and  the 
ratio  has  been  reduced  to  one  surprisingly  small.     To  the  debit  side  of  the  account  is 
charged  all  such  stops  as  are  caused  by  defective  construction  of  any  part  of  the  appa 
ratus.      The  number  of  these  has  heretofore  been  unreasonably  large.      First-class 
mechanical  construction  costs  but  little,  if  any,  more  than  such  as  would  not  pass  inspec- 
tion in  any  good  machine-shop,  and  gives  immeasurably  better  satisfaction  in  service. 
There  remain  a  certain  number  of  stops  due  to  "unknown"  causes,  and  certain  stops  due 
to  climatic  conditions,  unavoidable  accidents  to  the  apparatus,  derailments,  lightning, 
etc.,  which  are  grouped  by  themselves  under  the  head  of  "accidental."     Longer  experi- 
ence will  doubtless  suggest  ways  in  which  the  number  of  these  may  be  diminished. 

The  severe  tests  of  actual  service  under  all  varieties  of  climate  and  temperature  show 
that  the  perfect  railroad  signal  has  not  yet  been  invented.  In  each  system  certain  deficien- 
cies, or  failing  cases,  must  be  provided  against  in  order  that  the  signal  may  work  regu- 
larly or  be  used  with  safety. 

The  most  dangerous  error  an  automatic  signal  can  make  is  to  show  clear  when  a  train 
is  in  the  section.  The  Union  signal  is,  perhaps,  more  free  than  any  other  from  such  fail- 
ures, but  they  are  by  no  means  unknown.  The  cases  which  have  come  under  my  own 
observation  have  been  due  to  (1)  a  failure  of  the  track  circuit  relay  to  drop  its  armature 
when  the  current  was  shunted  out  of  the  magnet ;  (2)  too  much  battery  on  the  rail  circuit; 

(3)  crossed  wires  between  the  signal  and  overlap  relay  ;  (4)  failure  of  the  signal  magnet  to 
release  the  clockwork. when  the  circuit  was  opened  ;  or  (5)  the  sticking  of  some  mechanical 
part  of  the  apparatus  which  should  have  moved  freely.    Of  these  the  first  is  by  far  the 


AUTOMATIC  SIGNALS  ON  THE  BOSTON  &  ALBANY.  35 

most  common,  except  in  ice  and  sleet  storms  ;  like  the  fourth,  ii  is  usually  due  to  fixed 
magnetism  in  the  cores  or  armature  of  the  relay,  and  could  be  prevented  by  the  use  of 
better  iron  in  their  construction.  The  second  cause  is  the  fault  of  the  signalman,  and  the 
third  may  also  be.  This  last  may  be  remedied  by  a  different  arrangement  of  circuits, 
which  the  Boston  &  Albany  will  adopt  in  all  new  work.  The  fifth  may,  or  may  not,  be  the 
signalman's  fault.  A  rainstorm  sharply  followed  by  freezing  weather  wiil  stick  every 
signal  in  an  hour  in  the  position  it  happens  to  be  at  the  time.  A  heavy  fall  of  damp  snow 
will  sometimes  (but  rarely)  do  the  same  thing. 

Another  failing  case  of  bad  repute  is  when  the  signal  stands  clear  with  a  switch  open 
This  usually  shows  a  faulty  connection  in  the  switch-box.  There  is  no  way  (with  the  ar- 
rangement of  circuits  shown  in  figs.  2  and  3)  to  know  beforehand  whether  opening  the 
switch  will  set  the  signal.  A  far  safer  connection  is  shown  in  figs.  5  and  5a,  where  the 
current  in  the  rails  is  made  constantly  to  pass  through  the  switch -box,  when  the  switch 
is  on  the  main  line.  The  switch-box  must  be  in  good  order  or  the  current  cannot  pass. 
All  the  switch  connections  on  the  Boston  &  Albany  are  now  being  changed  to  this 
style.  * 

A  multitude  of  causes  may  make  a  signal  stand  at  "danger"  when  no  train  is  in  the 
section  or  switch  open.  Any  derangement  of  the  apparatus  (except  the  special  ones  enum- 
erated above)  or  interruption  of  the  rail  circuit  by  displacement  of  the  track  or  other- 
wise will  do  this.  Stops  thus  caused  are  principally  a  matter  of  annoyance  and  expense. 
They  do  not  introduce  an  element  of  danger,  except  that,  if  very  frequent,  they  would 
tend  to  make  enginemen  careless  of  the  indications  of  the  signal  when  it  did  warn  of  ex- 
isting danger.  Though  there  may  be  a  considerable  number  of  such  stops  in  a  month  on 
some  divisions  of  the  road,  it  is  found,  when  account  is  taken  of  the  number  of  trains  run- 
ning, that  the  ratio  of  failures  to  number  of  operations  is  very  small. 

The  cost  of  operating  each  Union  signal,  including  superintendence,  was,  during  the 
year  ending  Oct.  1,  1886,  about  $75.69,  or  $(3.31  per  month. 

There  are  roads  equipped  with  Union  signals  which  claim  to  have  fewer  unneces- 
sary s'ops  per  signal  than  the  Boston  &  Albany,  and  to  run  their  signals  at  less  expense, 
but  they  have  for  the  most  part  no  overlapping  sections  (which  would  very  greatly 
complicate  their  application);  their  trains  run  at  longer  intervals,  and  in  some  cases  the 
account  of  stops  and  their  causes  is  not  so  carefully  kept. 

*  The  current  in  the  rail  A  B,  when  the  main  track  is  unbroken,  must  normally  pass  through  the  points  X  Y'> 
when  the  switch  is  moved,  the  connection  between  X and  Fis  broken  and  the  opposite  rails  connected  (as  by  a  pair 
of  wheels)  through  Fand  Z. 


THE  WESTINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING. 

[December  21,  1888.] 

Before  entering  into  a  description  of  the  operation  of  this  system,  it  will  be  neces. 
sary  to  describe  the  construction  and  operation  of  its  several  parts.  There  are  a  steam- 
generating  boiler,  an  air  compressor,  and  a  condensing  tank  through  which  the  air  must 
pass  before  entering  the  main  air  pipe.  This  deprives  the  air  of  any  moisture  which  it 
may  have  had  originally,  or  collected  in  passing  through  the  heated  cylinder  of  the  com- 
pressor, and  prevents  its  collecting  in  the  valves  or  cylinders  where  it  might  interfere 
with  their  operation. 

Each  signal  blade  is  connected  directly  to  a  pneumatic  cylinder,  the  pressure  to 
which  is  controlled  by  a  small  valve  actuated  by  an  electro-magnet,  which  in  turn  is  con- 
trolled by  the  operator  in  the  cabin.  The  air  supply  to  each  of  these  cylinders  is  taken 
from  a  cylindrical  tank  at  the  bottom  of  the  post,  all  of  which  are  connected  directly  to 
the  main  air-pipe;  consequently,  all  signals  have,  at  all  times,  the  full  pressure  of  the 
compressed  air,  right  at  their  cylinder  valves.  The  control  of  this  pressure  by  the  elec- 
tric valve  and  the  valves  by  the  operator  will  be  treated  later. 

From  this  same  air  pipe  pressure  is  conducted  to  the  switch  valves,  where  it  is  stored 
in  a  reservoir,  which  forms  the  valve  support,  and  is  provided  with  a  cap  or  plug  with 
three  ports  formed  in  it,  and  a  D-valve  seated  over  them,  exactly  as  is  done  in  a  steam 
engine.  Encasing  this  D-valve  and  its  ports  (see  fig.  4,  A]  is  a  hollow  cap  fastened  to 
the  reservoir  and  connected  with,  it  so  that  the  full  pressure  from  the  reservoir  is  at  all 
times  in  it,  and  consequently  on  top  of  the  D-valve,  holding  it  seated.  One  of  these 
ports  connects  directly  to  the  open  air;  this  is  the  centre  one,  while  the  right  and  left 
ones  connect  each  to  one  end  of  the  cylinder  operating  the  switch.  This  D-valve  is  so 
constructed  that  it  is  impossible  to  admit  pressure  to  one  of  the  ports  before  having  con- 
nected the  other  with  the  exhaust.  Jt  is,  therefore,  very  evident  that  it  is  impossible  to 
have  pressure  on  both  sides  at  one  time,  and  also  that  the  full  air  pressure  is  always 
holding  the  switch  in  the  position  last  moved  to.  With  this  description,  it  will  be  clear 
how  the  pressure  can  be  changed  to  one  end  or  the  other  of  the  switch  cylinder. 

The  switch  movement  (fig.  5)  consists  of  a  long  cylinder,  5£  in.  in  diameter,  provided 
with  two  flanges  for  securing  it  to  the  ties,  and  two  studs  or  trunnions  on  the  opposite 
side  forming  pivots  for  an  arm  operating  the  lock  and  detector  bar  of  the  switch,  a  piston 


THE  WESTINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING.  37 

composed  of  a  plunger  packed  at  each  end  and  formed  into  a  rack  between,  engaging 
into  a  pinion  which  rotates  about  f  of  a  revolution  to  each  movement  of  the  rack  piston. 
This  pinion  is  keyed  fast  to  a  shaft  on  which  a  crank  is  formed,  and  turns  with  the  pinion. 
To  this  crank  the  operating  rod  of  the  switch  is  connected,  and  also  a  link  joining  it  to 
the  rod,  already  mentioned,  operating  the  lock  and  detector  bar.  It  will  be  noticed  that 
this  crank  stands  beyond  the  centre  line  of  its  axis  continued  through  the  centre  of  the 
switch  connection,  and  that  it  might  move  a  corresponding  distance  to  the  right  of  this 
centre  line  before  giving  any  appreciable  motion  to  the  switch  itself,  on  account  of  the 
small  arc  thus  described.  It  is  the  peculiar  arrangement  of  this  crank  that  renders  this 
movement  so  simple  in  effecting  the  motion  of  the  detector  bar  and  the  preliminary  un- 
locking of  the  switch  and  a  final  motion  of  the  bar  and  locking  of  the  switch  after  it  has 
been  moved.  By  reference  to  the  cut  it  will  be  clearly  seen  that  the  movement,  when 
normal,  holds  the  switch  locked  in  one  of  its  two  positions  and  the  detector  bar  below 
rail  level.  Also  that  the  first  motion  to  take  place  is  the  simultaneous  raising  of  the  bar 
and  unlocking  of  the  switch.  The  lock  bolt  thus  operated  is  of  sufficient  length  to  have 
been  fully  withdrawn  from  the  hole  in  the  lock  rod  of  the  switch  before  the  motion  of 
the  crank  is  imparted  to  the  rod  moving  the  switch.  It  is  also,  for  the  sake  of  simplicity, 
allowed  to  travel  still  farther  from  the  lock  rod  during  half  the  motion  of  the  switch, 
when  it  again  approaches  the  rod,  and  by  the  time  it  ar.rives  at  the  bar  again  the  switch 
must  have  moved  so  as  to  bring  the  second  hole  in  the  lock  rod  opposite  the  pin  before 
it  will  become  locked,  and  indicate  it  in  the  cabin  in  a  way  to  be  yet  described.  On  the 
casting  forming  a  guide  for  the  lock  rod,  directly  in  front  of  the  locking  pin,  is  placed  a 
circuit-controlling  device  (fig.  5,  A),  which,  when  the  lock  pin  has  entered  the  lock  rod 
of  the  switch,  holds  the  circuit  open,  and  when  the  pin  is  withdrawn  permits  it  to  be- 
come closed.  The  function  of  this  device  will  be  described  later. 

Having  described  the  construction  of  the  switch  valve,  we  will  explain  the  manner 
of  operating  it.  On  each  side  of  the  hollow  chamber  or  cap  encasing  the  D- valve,  (fig.  4, 
B)  are  two  small  cylinders  containing  pistons,  and  a  stem  from  each  extending  through 
a  stuffing-box  into  this  cap  or  chamber  and  resting  one  against  each  end  of  the  D-valve. 
Connected  to  the  heads  of  these  two  cylinders  are  two  small  pipes  which  run  directly  into 
the  cabin  and  to  the  machine,  where  they  run  to  the  ports  of  a  three-way  cock  operated 
by  the  switch  lever  (fig.  3,  A).  This  cock  is  identical  in  operation  with  the  D-valve,  in 
that  but  one  port  can  have  pressure  on  it  at  a  time,  the  only  difference  in  its  construc- 
tion being  that  its  seat  is  cylindrical,  or  rather,  conical,  instead  of  flat  on  a  horizontal 
plane,  as  in  the  D- valve.  It  is  evident  that  pressure  must  be  on  one  or  the  other  of 
these  small  cylinders,  (fig.  4,  B),  at  all  times.  It  is  also  evident  that  since  the  D-valve  is 
set  between  these  pistons,  any  motion  of  them  will  be  imparted  to  the  valve  also,  and 
that  the  pressure  on  each  piston  acts  against  the  other  one  through  the  valve,  thus  mak- 
ing the  two  pistons  and  the  D-valve  act  as  a  solid  plunger  in  a  single  cylinder.  The 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

way  connected  with  the  piston  stems,  but  simply  guided  between 
rdlcfaing  compensation  for  wear  on  the  seat  and  under  face  of  valve.  It  is 
fco  throw  two  or  more  switches  by  the  same  lever,  as  is  the  case  with  a  cross- 
with  movable  frogs.  In  such  cases,  unless  they  be  too  far  apart,  but  one 
,  and  each  one  of  the  two  or  three  switch  cylinders  is  connected  directly  to  it  in 
the  same  manner  as  is  done  with  a  single  one.  It  is  perhaps  necessary  to  explain  now  the 
necessity  of  this  valve  being  interposed  between  the  cock  at  the  machine  and  the  switch 
cylinder,  since  it  will  be  evident  that  the  operation  would  be  the  same  if  the  pipes  from  the 
machine  went  directly  to  the- switch  cylinder.  While  this  is  the  case,  still  a  serious 
feature  in  this  arrangement  prevents  its  adoption.  Owing  to  the  long  distance  it  is  often- 
times found  convenient  to  operate  switches  from  the  cabin  with  this  system,  and  the 
consequent  long  line  of  pipe  necessary  to  be  filled  with  air  and  exhausted  at  every  move- 
ment of  the  switch,  it  is  found  not  only  more  economical  in  saving  air,  but  very  much 
more  efficient  in  operation  to  place  this  valve  as  close  to  the  switch  or  switches  operated 
as  possible,  and  fill  the  small  pipes  leading  from  the  small  cylinders  of  the  valve  to  the 
machine  with  water  in  summer  and  chloride  of  calcium,  alcohol  or  some  other  non- 
freezing  liquid  in  winter.  When  this  is  done  and  the  air  from  the  machine  cock  is 
admitted  on  top  of  it,  it  instantly  acts  against  the  pistons  of  the  small  cylinders  of  the 
switch  valve,  fig.  4,  (7,  since  the  liquid  will  not  compress,  but  acts  as  a  solid  rod.  This 
would  not  be  the  case  were  the  air  used  alone,  since  it  would  require  some  time  to  com- 
press to  the  pressure  necessary  to  move  the  valve,  and  waste  a  corresponding  amount  by 
connecting  the  opposite  side  to  the  exhaust.  In  order  to  compensate  for  loss  of  liquid 
by  evaporation  or  leak,  an  automatic  filler  is  attached  to  all  hydraulic  pipes,  fig.  9,  which, 
normally,  is  opened  with  all  of  them  not  having  pressure  on  them,  and  automatically 
closed  from  them,  by  means  of  a  check  valve,  when  the  pressure  is  admitted  on  top  of 
the  water  in  them.  This  insures  a  full  supply  of  liquid  in  these  pipes  at  all  times,  and 
consequently  a  quick  action  of  the  switch  valve. 

The  cylinder  operating  the  signal  will  now  be  described.  As  before  stated,  this  cylin- 
der, fig.  8,  has  the  pressure  right  at  the  valve  controlling  its  admission  to  it.  This  is 
also,  controlled  by  an  electromagnet,  the  circuit  of  which  is  controlled  by  the  operator 
tb rough  the  machine.  The  piston  of  this  cylinder  is  connected  with  the  blade  either 
directly  or  through  a  balance  lever,  fig.  10,  and  in  its  normal  condition  is  in  the  upper 
end  of  the  cylinder,  being  held" there  by  the  counter- weight  blade  or  balance  lever.  In' 
this  position  of  the  piston  the  blade  is  in  the  horizonital  or  danger  position,  and  can  only 
be  moved  from  that  position  by  the  admission  of  air  on  top  of  the  piston,  thus  depressing 
it  sufficient  to  give  the  blade  the  proper  angle  (60°)  indicating  safety  or  caution,  accord- 
ing to  the  nature  of  the  signal.  This  is  accomplished  by  a  small  pin  valve,  fig.  8,  B, 
which  normally  holds  the  pressure  closed  from  the  cylinder,  and  the  cylinder  open  to 
the  exhaust.  When  operated  by  the  electromagnet  becoming  charged  from  a  current 


THE  WE3TINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING 


PLAN  OF  SWITCH  &  CONNECTIONS 

SWITCH  MOVEMENT. 

THE  WESTINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING. 


40  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

sent  through  it  by  the  operator,  the  reverse  condition  takes  place;  i.  e.,  the  pressure  is 
admitted  to  the  cylinder  on  top  of  the  piston,  and  the  exhaust  is  closed  completely.  The 
pressure  thus  confined  depresses  the  piston  and  operates  the  blade.  The  instant  the  cur- 
rent is  broken  in  the  magnet  the  armature  is  released  and  the  air  again  unseats  the  valve 
closing  the  exhaust,  and  again  cuts  off  the  pressure,  thus  allowing  the  signal  to  return  to 
danger.  This  cylinder  is  also  provided  with  a  circuit  breaker  controlling  the  current  to 
an  electric  lock  to  the  lever  operating  it,  fig.  8,  A.  The  construction  of  this  lock  will  be 
described  with  the  machine,  later.  This  circuit  is  closed  only  when  the  signal  is  in  its 
danger  position,  and  open  at  all  other  times  ;  and  since  the  lock  releases  the  lever  only 
when  the  current  is  on  it,  it  is  evident  that  the  lever  is  unlocked  only  when  the  signal  is 
in  the  danger  position.  Consequently  when  the  signal  is  cleared  the  lever  operating  it  is 
automatically  locked;  and  should  the  signal  fail  to  go  to  danger  after  the  circuit  has  been 
broken  by  the  lever  controlling  it,  that  lever  will  re  main  locked  electrically,  and  hold  all 
switches  locked  mechanically  over  which  that  signal  gives  right  of  way,  until  it  does 
return  to  danger. 

The  small  pot  or  drilling  signal,  fig.  6,  consists*simply  of  one  of  the  same  cylinders  as 
are  used  to  operate  the  semaphore  signals,  placed  horizontally  in  a  cast-iron  box  or  case 
and  connected  to  an  arm  keyed  fast  to  a  vertical  shaft  to  which  the  signal  target  and  lamp 
are  secured.  When  operated,  the  cylinder  turns  this  shaft  one-quarter  of  a  revolution, 
thus  changing  the  target  or  light.  The  opposite  side  of  this  arm  is  extended,  and  con- 
nected to  a  long  spiral  spring,  which  returns  the  signal  to  danger  when  cylinder  is  dis- 
charged. 

When  it  is  desired  to  operate  indicators  in  connection  with  the  signal,  a  device  is  pro- 
vided in  a  well-covered  box,  shown  to  the  right  of  fig.  10,  fastened  directly  under  the  signal 
blade  and  operated  by  it.  This  apparatus  is  provided  with  a  pair  of  electromagnets  for  each 
indicator  rod,  and  a  simple  means  of  throwing  one  or  the  other  of  these  rods  into  engage- 
ment with  the  signal,  by  them,  so  that  it  will  be  opened  rigidly  thereby.  The  number  or 
letter  (see  fig.  7)  displayed  when  the  signal  is  cleared  indicates  to  what  track  the  switches 
are  set.  This  system  of  signaling  is  of  advantage  in  yards  where  a  great  deal  of  drilling 
is  done,  on  account  of  its  simplicity  in  construction  and  operation,  the  small  number  of 
lamps  employed  and  the  ease  with  which  they  can  be  read.  When  the  signal  is  at 
danger  the  indicators  are  obscured  by  a  screen  which  hangs  in  front  of  them. 

It  is  necessary  here  to  explain  that  all  levers  controlling  signals  (fig.  2,  A}  when 
thrown  out  of  their  normal  (vertical)  position,  i.  e.,  to  the  right  or  left,  effect  the  locking 
of  switches  during  the  first  part  of  their  stroke,  and  close  the  circuit  on  the  signal  at  the 
end  of  the  stroke.  After  the  electric  locking  takes  place,  when  a  signal  has  been  cleared 
by  the  signal  lever  being  thrown  completely  to  the  right  or  left,  it  is  possible  to  throw  the 
lever  sufficiently  far  normal  again  to  break  the  circuit  to  the  signal,  but  not  far  enough 
to  release  the  locking  to  the  switches;  in  this  way  the  signal  must  go  to  danger  before  the 


THE  WESTINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING.  41 

switch  levers  can  be  released.  The  great  advantage  of  this  lies  in  the  fact  that  should 
a  signal  stick  at  safety,  it  indirectly  locks  all  switches  which  require  shifting  in  order  to 
set  a  signal  for  a  route  conflicting  with  it.  It  is  the  refore  impossible  to  give  two  con- 
flicting signals  at  any  time  by  mistake  or  improper  working  of  the  signals. 

The  interlocking  between  levers  of  the  machine  is  confined  to  that  between  switch 
and  signal  levers  only,  and  never  (unless  ordered  so)  between  switch  levers  themselves. 
Signal  levers  are  interlocked  between  each  other  through  the  switch  levers,  as  will  be 
described  next. 

Figs.  1,  2  and  3  will  make  clear  the  general  construction  of  the  machine,  and  it  is 
only  necessary  to  explain  that  the  framing  is  cast  iron,  the  levers,  valves,  locks,  etc, 
brass,  and  the  top  plate  of  hard  rubber,  as  are  the  rollers  lying  horizontally  over  it. 
Each  switch  lever  consists  of  a  small  brass  lever  keyed  at  the  centre  to  a  steel  shaft  which 
extends  through  a  bearing  formed  in  the  front  of  the  machine,  a  hard  rubber  roller  lying 
horizontally  over  the  top  plate,  and  terminates  in  the  three-way  cock  in  the  rear  of  the 
machine,  with  which  it  is  fastened  rigidly.  The  upper  end  of  this  lever  is  provided  with 
a  rubber  handle,  and  the  lever  end  extends  down  far  enough  to  just  clear  a  dog  or  latch 
(fig.  1,  A)  pivoted  loosely  under  the  machine,  and  extending  through  its  front  directly 
under  the  lever.  These  latches  perform  the  locking  of  the  switch  levers  by  the  signal 
levers.  In  the  normal  condition  of  all  signal  levers,  all  of  these  latches  lie  in  a  notch 
cut  in  the  locking  bars  (fig.  2,  It)  in  front  of  the  machine,  and  offer  no  obstruction  to  the 
movement  of  the  switch  levers ;  but  the  instant  a  signal  lever  is  moved  from  its  normal 
position,  the  latches  of  all  switches  affected  by  it  will  be  raised  so  as  to  cause  the  ends  of 
the  switch  levers  to  strike  them,  and  prevent  them  being  moved  far  enough  to  open  the 
valves  operating  the  switches. 

The  rubber  rollers  referred  to  as  forming  part  of  the  switch  and  signal  lever  spindles 
are  cast  rigidly  thereto,  and  provided  with  a  series  of  metallic  strips  or  collars  (fig.  3,  B] 
extending  part  way  round  them,  their  ends  terminating  each  in  one  of  the  six  slots  cut 
the  full  length  of  the  roller  parallel  with  its  axis.  These  strips  are  not  all  put  on  in  the 
same  relative  position  with  the  centre  line  of  the  operating  lever,  but  are  staggered,  so  as 
to  either  make  or  break  their  contact  with  the  upright  ends  of  the  strips  (fig.  3,  (7)  on  the 
rubber  plate  running  parallel  with  and  directly  under  them,  when  the  roller  is  rotated 
by  movement  of  the  switch  lever.  To  one  end  of  each  of  these  strips  on  the  rubber  plate 
the  controlling  wires  to  the  various  signals  run,  and  the  other  ends  are  joined  together 
and  run  to  one  common  battery  supplying  all  signals.  The  other  pole  of  this  battery  is 
connected  to  the  main  air  pipe,  which  is  used  as  a  common  return  for  all  circuits.  The 
breaks  in  each  one  of  these  strips  are  controlled  by  the  levers  operating  switches  over 
which  the  signal  thus  controlled  gives  right  of  way,  and  also  by  one  or  more  signal  levers, 
as  the  interlocking  may  require.  It  will  be  very  apparent  that,  before  the  current  to  any 
signal  can  be  established,  all  breaks  in  the  strip  carrying  its  current  must  be  closed  by 


42  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

the  bands  or  collars  on  the  rollers  making  contact  between  them.  This  is  done  by 
placing  the  levers  in  a  position  to  properly  set  all  switches  for  that  signal.  It  will  be  also 
evident  that  in,  having  moved  a  switch  lever  to  close  the  strip  for  one  signal,  it  will  at 
the  same  time  break  the  circuit  at  a  strip  controlling  another  signal,  requiring  that 
switch  in  its  original  position.  In  this  way  a  very  simple  and  effectual  interlocking 
between  signals  is  accomplished. 

The  strips  on  the  rollers  are  so  arranged  that  they  make  contact  between  the  upright 
strips  only  when  the  levers  are  in  their  extreme  positions,  one  way  or  the  other.  In 
order  to  be  able  to  move  a  switch  lever  from  one  side,  to  the  extreme  stroke  on  the  other 
side,  and  thereby  close  the  circuit  for  another  signal  requiring  that  switch  reversed,  with- 
out any  certain  knowledge  that  the  switch  has  moved,  a  device  is  attached  to  the  rear 
end  of  the  roller,  which  consists  of  a  quadrant  (fig.  3,  D)  secured  to  the  roller  by  a-  set 
screw,  and  having  cut  through  it  above  the  roller  a  radial  slot  through  which  projects 
horizontally  a  peculiarly  shaped  locking  lever,  provided  with  a  small  latch  or  tongue 
pivoted  near  its  centre,  and  capable  of  a  horizontal  movement  right  and  left  on  its  pivot, 
but  held  in  a  central  position,  parallel  with  the  lever  on  which  it  is  pivoted,  by  a  flat 
spring  on  each  side.  This  latch,  like  the  lever,  extends  through  the  slot  in  the  quadrant 
and  ends  flush  with  the  end  of  the  lever.  The  lever  with  the  latch  thus  arranged  is 
pivoted  in  a  suitable  bracket  fast  to  the  machine,  and  connected  at  its  far  end  with  the 
armature  of  an  electro-magnet  (fig.  3,  _Er),  the  circuit  to  which  is  controlled  directly  by 
the  lock  pin  of  the  switch  movement.  This  circuit  is  normally  open,  i.  e.,  when  the 
switch  is  locked,  and  closed  during  its  operation.  The  armature  of  the  magnet,  there- 
fore, normally  hangs  by  gravity  away  from  the  magnet  and  keeps  the  end  of  the  lever, 
projecting  through  the  quadrant,  elevated,  so  that  a  small  steel  pin  in  the  centre  of  the 
upper  inside  slot  of  this  quadrant,  when  the  switch  lever  is  thrown  beyond  the  vertical 
position,  strikes  the  latch  or  tongue  and  carries  its  free  end  with  it  as  far  as  its  con- 
struction will  permit ;  the  lever  then  will  have  been  moved  sufficiently  far  to  have  oper- 
ated the  valve,  and  consequently  moved  the  switch,  but  not  far  enough  to  have  made  the 
contact  between  the  strips  controlling  the  signal.  Before  this  is  possible  the  switch  must 
have  been  unlocked,  moved,  and  then  locked  in  the  other  position.  The  unlocking  of 
the  switch  closes  the  circuit  on  the  magnet,  which  becoming  charged  depresses  the  end 
of  the  lever  projecting  through  the  quadrant,  into  a  recessed  portion  of  the  radial  slot, 
holding  the  switch  lever  still  locked  thereby.  At  the  same  time,  the  small  latch  or  tongue 
being  thrown  below  the  small  pin  which  had  carried  it  out  of  its  central  position,  flies 
back,  under  the  pin,  into  its  central  position  on  the  other  side  of  the  pin.  The  latch  and 
lever  assume  this  position  as  long  as  the  switch  remains  unlocked,  but  on  being  locked  in 
the  position  moved  to  by  the  lever  being  reversed,  the  circuit  is  broken  on  the  magnet 
and  the  quadrant  end  of  the  locking  lever  is  raised  from  the  recess  in  the  quadrant  and 
the  lever  thus  unlocked  is  free  to  be  moved  to  the  end  of  its  stroke,  when  the  signal  cir- 


THE  WESTINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING. 


43 


cuit  becomes  closed.  Thus  the  closing  of  the  signal  circuit  depends  directly  on,  not  only 
the  movement  of  the  switch,  but  the  locking  of  it  after  it  has  moved.  The  electric  lock- 
ing of  signal  levers  is  effected  by  a  similar,  but  simpler  device,  which  consists  of  an  elec- 
tromagnet whose  armature,  like  that  of  the  indication  magnet,  is  connected  to  a  hori- 
zontal lever,  fig.  3,  F,  pivoted  in  its  centre,  and  its  far  end  projecting  through  a  locking 
quadrant  fast  to  the  roller,  and  engaging  in  such  a  manner  as  to  lock  it  from  being  moved 
out  of  its  centre  position,  if  normal,  or  from  being  put  normal,  and  thus  release  the 


Fig.  3. 
THE  WESTINGHOUSE  SYSTEM  OF  PNEUMATIC  INTERLOCKING. 

switches  locked  by  it,  if  out  of  its  centre  position,  when  the  current  to  the  magnet  is 
broken  through  the  circuit  breaker  of  the  signal  controlled  by  that  lever  being  at 

safety.  ,     ,, 

Directly  above  the  machine  is  placed  a  miniature  model  of  the  tracks  t  operated,  fig. 
3  G  and  small  movable  switches  thereon  are  connected  directly  to  the  rubber  roller,  so 
that  'after  the  indication  from  the  switches  is  received,  and  the  roller  turned  as  far  as 
possible,  these  small  switches  assume  the  position  of  the  corresponding  onps  on  the 
ground  In  this  way  the  operator  can,  at  a  glance,  see  the  condition  of  his  tracks  at  .any 


44 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 


time.  In  order  to  prevent  an  operator  by  mistake  throwing  his  signal  back  to  danger, 
and  then  his  signal  lever  normal,  and  finally  a  switch,  thus  released,  under  or  in  front  of 
a  passing  train,  an  interlocking  relay,  fig.  3,  H,  is  included  in  the  controlling  signal  and 
locking  circuits,  which,  after  the  operator  gives  the  signal,  places  the  lever  thus  locked 
out  of  his  control,  in  so  much  that  while  he  has  the  power  to  throw  the  signal  to  danger 
at  any  time,  it  is  not  in  his  power  to  throw  it  normal  and  release  the  switches  until  the 
train  has  passed  over  the  route  set  for  it  and  cleared  the  last  point  of  danger. 

When  within  about  one  mile  of  the  crossing,  junction,  yard,  or  of  whatever  the  tracks 
interlocked  consist,  an  approaching  train  automatically  drops  an  annunciator  on  the  rear 
of  the  track  model,  so  as  to  display  through  an  opening  in  the  model  board,  fig.  3,  /,  a 
number  or  letter  designating  the  track  on  which  the  train  is  approaching.  At  the  same 
time,  a  bell  begins  to  ring,  and  continues  to  do  so  until  the  train  has  passed  over  the  short 
insulated  section  provided  for  that  purpose,  fig.  3,  J.  These  drops  are  restored  to  their 
normal  (obscure)  position  by  a  blast  of  air  controlled  by  a  small  valve,  fig.  3,  K,  in  the 
front  board  of  the  machine,  by  the  operator. 

The  advantages  this  system  possesses  over  all  others  are  numerous.  Space  required 
is  limited,  thus  reducing  size,  and  therefore  cost  of  towers.  The  work  is  light,  conse- 
quently female  operators  can  be  employed,  thus  reducing  expenses.  It  gives  great 
facilities  for  special  locks.  Large  yards  can  be  worked  from  one  tower,  as  distance  is  of 
little  object,  switches  half  a  mile  away  working  as  well  as  those  close  to  the  tower.  There 
is  no  danger  of  signals  being  left  at  safety,  as  the  machine  remains  locked  until  the  signal 
lias  returned  to  danger.  Any  number  of  switches  can,  if  necessary,  be  worked  from  one 
lever. 

The  following  table  shows  the  plants  now  in  service: 

Pneumatic  Interlocking  Systems  in  Operation. 


Levers. 

Location. 

Railroads. 

Put  in  service. 

6                

Bound  Brook,  N.  J  

Phil.  &  Read,  and  L.  V  

1884. 
1884. 
1884. 
1884. 

1884. 
1884. 
1884. 
1885. 
1885. 
1885. 
1888. 
May  6,  1888. 
Aug.  19,  1888. 

6                 

Brightwood    Ind  

I.  V.  andC.,C.,  C.  &I.  

12m 
12 
6 

12  ol 
14 
24 
10 
6 
24  n 
24 
*24 

!W  St] 

d  stv 
wst; 

rle    

W^ilkinsburg   Pa         

Pennsylvania  

East  Liberty   Pa  . 

Pen  nsylvania  

Valparaiso   Ind  

Chic.  &  Grand  Trunk,  P.,  F.  W.  &  C.  and  N.  Y. 
C  &  St.  L  

e      

Stock  Yards  Chicago  

C  B  &  Q  and  Stock  Yard  R.  R  

Erie,  Pa  
Oakland  Cal    

L.  S.  &  M.  S.  and  Erie  &  Pitts  

S.  Pac.  R.  R.  Tower  No.  1  



"        '•           "      No.2  

«           n 

"         "           "      No.3  

le 

K           « 

"        "for     "      No.  1,  shipped  Dec.  8  

17th  st  Pitts.  Yd  

Pennsylvania  ,  

14th  st.           "       

*At  the  14th  St.  Pittsburgh  Yard  tower,  the  highest  number  of  movements  in  24  hours  is  1,500,  and  the  highest 
number  of  movements  in  one  hour  is  86.    The  machine  is  operated  by  one  man. 


AUTOMATIC  BLOCK  SIGNALS  ON  THE  PENNSYLVANIA. 


[August  23,  1889.] 

The  Union  Switch  &  Signal  Company's 
rail-circuit  system  of  block  signaling  is 
now  in  use  on  six  miles  of  the  four-track 
road  of  the  Pennsylvania  main  line  east 
of  Pittsburgh.  The  system  has  been  in 
use  between  Wilkinsburg  and  East  Lib- 
erty, about  2£  miles,  for  5£  years,  with  a 
high  degree  of  success,  and  it  is  this  that 
has  led  the  company  to  equip  the  addi- 
tional 3f,  miles.  This  latter  portion  of  the 
road,  from  East  Libery  westward,  is  shown 
in  the  sketch  given  herewith,  and  the  sig- 
nals upon  it  were  put  in  operation  on 
August  8. 

As  will  be  observed  from  the  drawing, 
the  signals  are  here  arranged  on  the 
original  plan  as  shown  in  models  ex- 
hibited several  years  ago ;  that  is,  the 
blocks  are  short,  averaging  half  a  mile  in 
length,  and  each  stop  or  home  signal  has 
a  distant  or  caution  signal,  which  caution 
signal  is  placed  upon  the  same  post  with 
the  stop  signal  of  the  preceding  block  sec- 
tion. This  simplifies  the  system  for  the 
engineer,  reducing  the  number  of  local- 
ities that  he  must  watch  for,  and  also  obvi- 
ously simplifies  the  arrangement  of  the 
posts  and  apparatus.  The  distance  between 
each  caution  signal  and  its  corresponding 


46  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

stop  signal  is  ample  for  bringing  a  train  to  a  stop,  and  with  caution  signals  for  every 
block  section  on  the  open  road  the  engineman  may  run  at  full  speed  on  the  most  obscure 
portions  of  the  road  or  in  the  densest  fog,  with  the  assurance  that  the  signals  will  always 
give  him  at  least  the  length  of  one  block  in  which  to  stop,  after  he  has  passed  the  post. 

Instead  of  "banner"  or  "gridiron"  signals  operated  by  clock  work  (the best  known 
form,  and  the  one  in  use  on  the  Boston  &  Albany,  Old  Colony  and  other  New  England 
roads),  the  semaphore  is  used,  and  the  power  for  moving  the  arms  is  compressed  air.  The 
apparatus  is  the  same  in  its  general  features  as  that  used  to  operate  semaphores  in  the 
pneumatic  interlocking  system,  described  in  a  previous  chapter  (pages  37-44).  A  pipe  ex- 
tends along  the  roadway  the  whole  six  miles  from  Pittsburgh  to  Wilkinsburg,  furnishing 
air  not  only  for  the  block  signals,  but  also  for  the  interlocking  apparatus  at  four  towers 
The  distant  signals  are  connected  to  the  stop  signals  by  a  line  wire  on  poles.  The  signals 
are  arranged  to  go  to  danger  after  the  engine  of  a  train  passes  them.  A  train  stopped 
by  a  home  signal  may,  after  waiting  two  minutes,  proceed  with  caution,  expecting  to 
find  a  train  on  the  block  aheap  or  switches  not  properly  set. 


ELECTRIC    APPARATUS    FOR    AUTOMATIC    BLOCK    SIGNALS. 


[September  G,  1889.] 

Following  is  a  plan  showing  the  arrangement  of  the  batteries,  electromagnets  and 
wires  used  in  operating  the  signals  described  in  the  preceding  chapter.  The  diagram 
shows  three  sections  of  four-track  road,  and  the  signals  are  arranged  in  the  natural  order 
as  related  to  the  tracks.  That  is,  taking  post  /  for  example,  and  looking  in  the  direc- 
tion the  train  is  moving,  the  two  right-hand  arms  are  for  track  F 1,  and  stand  at  danger 
to  protect  the  train  on  the  section.  The  left-hand  arms  are  for  track  F  2,  and  show 
all  clear,  the  section  being  unoccupied.  The  normal  position  of  arms  is  horizontal- 
danger— as  on  a  failure  of  battery  or  other  apparatus  they  automatically  assume  that 
position  ;  but  their  usual  position  is  down— safety— as  at  all  times  when  the  track  is 


Switch  box 


-M, 


Su/ilch  box 


JBf 


ARRANGEMENT    OF     ELECTRIC    CIRCUITS    FOR    THE    UNION    SWITCH    &    SIGNAL    COMPANY'S    PNEUMATIC 

AUTOMATIC   BLOCK   SIGNALS. 

clear  the  power  which  works  the  arms  is  in  operation  to  hold  them  down.  The  cross- 
over from  track  8  to  track  4  in  section  C  is  shown  in  position  to  lead  trains  from  the 
passenger  to  the  freight  track  ;  this,  it  will  be  observed,  breaks  the  circuits  in  both 
main  tracks  and  throws  to  danger  all  the  arms  on  post  c,  as  well  as  the  distant  signals 
for  the  same  section,  which  are  on  post  b.  The  method  of  connecting  the  circuit 
breaker,  located  in  the  switchbox,  was  illustrated  in  the  fiailroad  Gazette  of  June  24 
1887.  (See  page  31.) 

The  arrangement  of  the  electric  circuits  can  best  be  understood  by  following  out  the 
connections  for  a  single  section,  say  B\     At  the  east  end  of  this  section  is  the  battery, 


48  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

of  which  one  pole  is  connected  to  each  rail.  The  track  being  unoccupied,  the  current 
flows  through  the  rails  to  relay  y,  closing  it.  This  closes  the  circuit  through  the  local 
battery,  and  causes  the  electromagnet  in  the  pneumatic  signal  cylinder  B*  to  actuate 
the  air  valve  therein  and  pull  down  the  arm  IP  on  post  b.  It  will  be  understood  that 
the  cylinders  A\  B*,  (74,  D\  shown  in  the  engraving  on  an  enlarged  scale,  are  located 
upon  the  post  with  their  respective  arms. 

In  the  diagram  the  pneumatic  cylinders  and  the  semaphore  arms  are  lettered  and 
numbered  to  correspond  with  the  track  section  to  which  they  belong.  The  circuit 
through  pneumatic  cylinder  B^  is  carried  by  a  line  wire  L  on  poles  to  the  distant  signal 
for  the  same  section,  located  on  post  a,  and  the  current  operates  to  pull  down  that  signal 
also.  All  the  circuits  through  the  pneumatic  cylinders  terminate  in  the  ground  (6r).  If 
now,  a  train  enters  section  .A4  from  the  west  it  opens  relay  X,  and,  through  cylinder 
J.4,  throws  to  danger  the  home  semaphore  A4  on  post  a.  Strictly  speaking,  this  need 
not  be  allowed  to  affect  arm  B*  on  post  a,  as  that  arm  gives  an  indication  for  section 
B*  and  not  for  section  A* ;  but  to  simplify  the  indications  for  the  engineer  and  to 
obviate  even  an  appearance  of  inconsistency,  the  opening  of  the  circuit  through  cylinder 
A*  is  made  to  open  that  through  the  cylinder  shown  to  the  left  of  it,  which  actuates 
distant  signal  B^  on  post  a  just  referred  to.  This  opening  is  accomplished  by  a  circuit 
breaker  at  the  left-hand  end  of  cylinder  A\  by  which  the  current  from  wire  L  is  turned 
to  the  ground  before  it  reaches  cylinder  B*.  Thus  a  train  on  a  section  always  keeps 
horizontal  both  of  the  arms  that  are  immediately  behind  it.  Of  the  two  arms  on  any 
one  post,  an  engineer  may  find  the  home  arm  down  and  the  distant  arm  up,  as  is  shown 
on  post  e  for  track  1 ;  bu-t  he  will  never  find  the  home  arm  up  and  the  distant  arm 
down,  although  such  a  combination  will  involve  no  danger  if  the  indication  of  the  home 
arm  is  obeyed. 


AUTOMATIC  SIGNALS  ON  THE  FITCHBURG  RAILROAD. 

[June  15, 1888.] 

The  Fitchburg  was  the  first  to  adopt  the  Union  rail-circuit  signals  for  any  except 
experimental  purposes.  Ten  miles  of  this  road  were  equipped  with  the  old-style  instru- 
ments of  this  system  about  1879,  and  gradual  extensions  have  been  made  since  that  time. 
The  arrangement  of  batteries,  relays,  etc.,  for  these  signals  is  exactly  like  that  described 
in  the  article  on  "Automatic  Signals  on  the  Boston  &  Albany"  in  the  Railroad  Gazette 
for  June  24,  1887  ;  that  is,  at  the  end  of  the  section  farthest  from  the  signal  is  placed  a 
battery  having  its  poles  connected,  one  to  each  rail,  while  at  the  end  nearest  the  signal 
is  a  relay  with  its  coils  connected  in  like  manner,  one  pole  to  each  rail.  This  relay  opens 
and  closes  the  circuit  of  a  local  battery,  which  governs  the  movements  of  the  signal.  The 
only  difference  between  the  two  systems  is  in  the  form  of  the  signal — which  is  here  a 
semaphore  arm — and  the  motive  power,  which  is  compressed  air  moving  a  piston  in  a 
closed  cylinder.  Each  signal  is  placed  about  200  feet  from  the  beginning  of  the  section, 
in  order  that  the  engineers  may  see  them  operate,  and  is  provided  with  an  overlapping 
circuit  of  about  1,000  feet  in  length,  as  described  for  the  system  referred  to. 

In  1883  twelve  miles  of  the  eastbound  track  on  a  60-foot  grade  from  As~hburnham  to 
Fitchburg  were  equipped  with  electro-pneumatic  semaphores  by  the  Union  Switch  &  Sig- 
nal Company.  The  sections  are  about  a  mile  in  length.  The  general  appearance  of  the 
signal  is  shown  by  fig.  1.  At  the  top  of  an  iron  post  about  24  ft.  high  is  placed  the  sema- 
phore arm,  which  moves  about  60  deg.  in  a  vertical  plane  in  the  ordinary  manner.  The 
arm  itself,  however,  instead  of  being  connected  to  a  distant  lever,  is  attached  to  a  rod 
about  3  ft.  long  which  ends  in  a  yoke  or  stirrup.  In  the  yoke  is  a  box  containing  an 
electromagnet  and  a  closed  cylinder,  fixed  to  the  iron  post,  within  which  works  a  piston 
actuated  by  compressed  air.  The  section  of  this  cylinder  is  shown  in  fig.  2.  The  air  is 
supplied  through  a  feedpipe  P.  The  valve  admitting  it  to  the  cylinder  is  controlled  by 
an  electromagnet  which  is  so  arranged  that  when  the  current  circulates  in  the  coils  the 
armature  is  attracted  and  the  valve  is  held  open,  admitting  the  air  to  the  cylinder.  This 
drives  the  piston  before  it  to  the  bottom  and  brings  down  the  blade.  When  for  any 
cause  the  current  is  interrupted,  the  valve  closes,  the  exhaust  is  opened,  and  the  air  es- 
capes; a  counter-weight  brings  the  signal  to  danger. 


50  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

Below  and  in  front  of  the  piston  rod  is  seen  an  electric  circuit-closer  attached  to  a  small 
spindle,  independent  of  the  piston  rod,  but  which  is  operated  by  the  piston  itself,  when 
its  own  movement  toward  the  bottom  of  the  cylinder  is  nearly  completed.  This  is  so 
adjusted  as  to  keep  the  auxiliary  circuit  which  it  governs  closed  whenever  the  signal  is 
$IT£'el%aTj-  Conveying  the  indication  of  this  fact  to  any  desired  distance;  it  may  also  be 
a'rranged-.to^ing  a  bell  or  give  other  warning  whenever  the  signal  shows  danger.  The 
ipo^jetnent'of  the  circuit- closing  device  is  made  to  depend  on  that  of  the  piston  in  such  a 
manner  .!%<t  the  completed  movement  of  the  piston  [and  so  of  the  signal]  must  take  place 
Jt>ef dfe  4he  auxiliary  circuit  will  be  closed  (or  opened,  as  the  case  may  be).  On  the  Fitch- 
buig  tliis  is  made  use  of  only  in  the  case  of  a  few  special  signals,  to  ring  a  bell  at  certain 
switches  from  which  the  signal  cannot  be  seen  or  to  warn  switchmen  when  a  train  has 
entered  the  section. 

The  compressed  air  at  60  Ibs.  pressure  is  supplied  by  a  pump  located  at  Fitchburg. 
This  pump  is  automatic  and  similar  in  principle  to  that  employed  for  the  Westinghouse 
air  brake.  The  air  passes  tirst  through  a  coil  of  pipe  to  cool  it,  thence  into  a  reservoir, 
with  which  is  connected  a  blow-off  cock  to  remove  the  condensed  water.  The  air  from 
this  reservoir  passes  into  a  1-in.  pipe  running  between  the  tracks  about  1|  ft.  below  the 
surface.  At  bridges,  etc.,  where  it  comes  to  the  surface,  expansion  and  contraction  are 
provided  for  by  a  long  bend  or  a  round  turn  in  the  pipe.  At  each  signal  a  J-in.  branch 
is  connected  with  the  main  pipe.  This  leads  to  a  reservoir  at  the  bottom  of  the  post, 
which  holds  air  enough  to  operate  the  signal  about  a  dozen  times.  There  is  a  stop- cock 
in  this  branch,  which  can  be  closed  should  occasion  require.  Stop-cocks  are  also  in- 
serted in  the  main  pipe  about  every  half-mile  for  the  purpose  of  locating  and  confining 
any  trouble  with  the  main  pipe  to  a  small  section,  so  that  only  one  or  at  most  a  few  sig- 
nals need  be  affected.  From  the  reservoir  at  the  bottom  of  the  post  a  £-in.  pipe  runs  to 
the  air  cylinder  operating  the  signal,  and  when  the  valve  is  open  the  pressure  brings  the 
signal  clear.  The  electromagnet  is  in  the  circuit  of  a  local  battery,  which  is  controlled 
by  a  relay,  the  coils  of  which  are  connected  to  the  rails  as  in  the  clockwork  signals. 
When  a  train  enters  the  section  this  relay  opens  the  local  circuit,  the  armature  of  the 
signal  magnet  falls  off  and  closes  the  valve  leading  to  the  cylinder  and  opens  an 
exhaust.  The  air  escapes  and  the  signal  arm  takes  a  horizontal  position  until  the  section  is 
clear.  The  same  thing  happens  if  the  batteries  fail  or  a  wire  or  rail  breaks.  Duplicate 
pumping  apparatuses  located  at  the  other  end  of  the  grade  (Ashburnham),  so  that  in  case 
of  accident  or  repairs  to  the  pump  at  Fitchburg,  or  a  break  in  the  main  pipe,  the  signals 
can  be  worked  from  the  other  end  as  far  as  the  break,  for  an  indefinite  time.  The  air  in 
the  auxiliary  reservoir  at  the  signal  posts  is  also  sufficient  for  a  number  of  operations. 

It  is  not  necessary  to  run  the  pump  for  these  signals  more  than  three  or  four  hours 
per  day,  and  as  much  during  the  night.  The  regular  work  of  the  engineer  is  to  run 
hoisting  machinery  for  a  coal  dump  ;  in  addition  to  this  he  runs  the  pumps  for  the  sig- 


AUTOMATIC  SIGNALS  ON  THE  FITCHBURG  RAILROAD. 


51 


nals  occasionally  until  the  air  pressure  reaches  601bs.;  then  he  stops  until  it  falls  to  about 
401bs.,  when  he  pumps  again. 

The  number  of  operations  of  these  sig- 
nals for  two  months  in  1887  was  48,487,  or 
about  795  per  day.  The  number  of  failures 
in  the  same  period  was  133,  or  one  failure  to 
365  operations;  22  disk  signals  during  the 
same  pe'iod  made  69,844  operations,  and 
there  were  54  failures,  or  one  in  1,293  opera- 
tions. The  cost  of  12  electromagnet  sema- 
phores with  the  necessary  pumping  appar- 
atus, etc.,  was  $11,126,  or  $927.17  per  signal. 
The  cost  of  14  disk  signals  erected  in  1887 
for  another  railroad  was  $6,971,  or  $497.94  per 
signal. 

The  cost  of  maintenance  of  the  electro- 
pneumatic  signals  is  about  $133.33  per  signal 
per  year;  that  of  clockwork  disk  signals  about 
$75  per  year  each  signal. 

The  application  of  these  signals  in  a  con- 
siderably more  complicated  form  was  made 
on  13  miles  of  the  West  Shore  road  in  1884. 
The  same  system  was  applied  to  short  sec- 
tions of  the  Pennsylvania  and  some  other 
roads  about  the  same  time.  In  this  arrange- 
ment each  block  signal  was  provided  with 
a  distant  signal  at  the  beginning  of  the  pre- 
ceding section,  so  that  there  were  on  each 
post  two  signals,  the  upper  of  which  was 
painted  red  and  referred  to  the  section  begin- 
ning at  the  signal,  and  the  lower,  which  was 
green  and  cut  with  a  dovetailed  end,  belonged 
to  the  section  second  in  advance  of  where 
the  signal  stood.  Each  block  signal  was  con- 
nected with  its  distant  signal  by  a  wire  cir- 
cuit, so  that  the  latter  reproduced  all  the  move 

ments    Of     the     former.        Besides    this,    each       Electro-Pneumatic  Block  Signal,  Fitchburg  Railroad. 

red  signal  when  in  the  danger  position  was  caused  to  close  a  shunt  circuit  around  the 
magnet  of  the  green  signal  on  the  same  post,  so  that  the  latter  also  stood  at  danger  as  long  as 


Fig,  2. 


52  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

a  train  was  in  the  section.  There  were  thus  three  signals  at  danger  behind  a  train,  two  at 
the  beginning  of  the  section  where  the  train  was,  and  one  at  the  beginning  of  the  pre- 
ceding section.  They  were  lighted  at  night  by  lamps  which  showed  red  when  the  signals 
were  in  the  stop  position,  and  green  for  all  clear.  If  a  train  found  the  two  arms  on  any 
post  standing  at  danger,  or  two  red  lights  at  night,  it  would  indicate  that  the  section  be- 
ginning at  the  post  was  obstructed,  while  the  upper  arm  inclined  and  the  lower  one 
horizontal  (or  at  night  a  green  light  with  a  red  one  below  it)  would  mean  that  the  section 
immediately  in  advance  was  clear,  but  a  train  or  other  obstruction  must  be  looked  for 
on  the  second  section  ahead. 

This  was  the  first  extensive  application  of  electro-pneumatic  semaphores  put  up  by 
the  Union  Switch  &  Signal  Company,  and  they  were  then  without  that  knowledge  of  the 
proper  methods  of  construction  and  operation  which  has  been  since  gained  by  experience. 
Partly  from  this  cause,  and  partly,  it  is  claimed,  because  the  road  was  new  and  the 
settlement  and  displacement  of  the  roadbed  caused  many  leaks  in  the  pipes,  this  system 
never  gave  complete  satisfaction,  and  has  now  been  discontinued,  the  semaphores  being 
worked  by  signalmen  and  without  distant  signals. 


THE  HALL  BLOCK  SIGNAL. 


{September  12, 1890.] 

The  illustrations  herewith  show  the  apparatus  used  in  Hall's  electric  automatic  block 
system.  The  Hall  is  a  wire  circuit  system,  the  circuit  being  normally  closed.  The  signal 
is  a  circular  disk  of  silk  stretched  upon  an  aluminum  ring  and  inclosed  within  a  wooden 
case  with  a  glass-covered  opening.  The  front  of  this  case  being  painted  dark  and  show- 
ing some  10  square  feet  of  surface  to  an  approaching  engineman,  the  signal  is  a  con- 
spicuous object.  Fig.  1  shows  the  arrangement  of  wires  and  electromagnets  for  operat- 
ing a  simple  block-signal  circuit.  At  the  entrance  of  the  section  is  located  the  "block  " 
track  instrument,  O  S,  the  operation  of  which  sets  the  signal  at  danger.  The  similar 
instrument  at  the  other  end,  0  S,  is  called  the  "clear"  track  instrument,  its  function 


o-s. 


THE  HALL  AUTOMATIC  BLOCK  SIGNAL-DIAGRAM  OF  ELECTRIC  CIRCUITS— Fig.  1. 

being  to  restore  the  signal  to  the  safety  position.  These  two  instruments  are  alike  in 
principle  and  construction,  except  that  the  clear  instrument  stands  normally  open,  while 
the  block  instrument  stands  normally  closed.  The  "clear"  track  instrument  is  located 
1,500  or  2,000  feet  beyond  the  end  of  the  section,  so  that  the  longest  train  will  be  wholly 
clear  of  the  section  before  the  foremost  wheel  touches  it,  though  the  circuits  are  so 
arranged  that  the  signal  does  not  go  to  the  safety  position  until  the  whole  of  a  passing 
train  goes  over  the  instrument. 

It  is  the  relay  and  JTthe  battery.  They  may  be  located  at  any  point  within  the 
block.  D  is  the  signal  disk,  described  more  fully  in  connection  with  figs.  2  and  3.  The 
circuit  is  normally  closed,  and  signal  D  is  held  in  the  position  shown  (safety),  by  the 
force  of  the  electromagnet,  the  circuit  being  completed  from  the  battery  X  through  wire 
1,  track  instrument  C  S,  wires  2  and  3,  electromagnet  S,  wire  4,  contact  point  p,  wire  5, 
electromagnet  r,  wire  6,  to  battery.  A  train  in  entering  the  section  opens  this  circuit,, 


54 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 


the  first  wheel  of  the  train  breaking  the  contract  between  the  spring  and  its  anvil  C  S; 
electromagnets  r  and  s  are  demagnetized,  signal  D  falls  to  a  position  in  front  of  the 
glass-covered  opening  (to  danger),  and  the  contact  at  p  is  broken.  After  the  whole  of 


Hall  Signal— Fig.  2. 


Hall  Signal  Inst-ument — Fig.  3. 

the  train  has  passed  over  the  "block"  instrument,  the  contact  between  the  spring  and 
its  anvil  will  be  restored  ;  but  as  the  circuit  is  now  broken  at  p,  the  signal  will  remain 
down  (at  danger)  until  the  points  atp  are  again  brought  in  contact ;  that  is,  until  the 


THE  HALL  BLOCK  SIGNAL.  55 

train,  in  passing  out  of  the  section,  completes  a  circuit  that  shall  energize  electromagnet 
r.  This  is  accomplished  by  the  closing  of  the  spring  of  the  "clear "  track  instrument  O 
#,  which  completes  a  circuit  from  battery  X  through  wire  7,  spring  and  anvil  at  0  8 
wire  8,  electromagnet  r,  wire  6,  to  the  battery.  The  contact  at^>  is  now  closed,  and  the 
signal  circuit  is  complete,  but  the  signal  will  remain  at  danger  until  the  train  has  entirely 
cleared  the  "clear  "  track  instrument,  from  the  fact  that  as  long  as  the  spring  at  0  S  is  in 
contact  with  its  anvil  two  circuits  are  completed,  one  through  the  clear-track  instrument 
and  the  relay  magnet  and  the  other  through  the  block  track  instrument,  signal  magnet 


Hall  Track  Instrument — Fig.  4. 

and  relay  magnet.     This  divides  the  battery  power  and  leaves  S  too  weak  to  lift  the 
disk. 

Fig.  2  is  a  view  of  the  case  which  contains  the  signal  instrument.  A  white  reflector 
in  or  behind  the  case  is  exposed  through  the  glass-covered  aperture  as  long  as  the  red 
disk  is  held  out  of  sight.  The  front  of  the  case  being  dark,  safety  is  thus  shown  by  a 
white  disk  in  the  midst  of  a  dark  ground.  The  falling  of  the  red  disk  before  the  glass 
produces  the  danger  signal.  At  night  a  lamp  is  placed  between  the  reflector  and  the 
disk,  so  as  to  illuminate  the  latter  when  it  is  down  and  to  show  clear  (white)  when  the 
disk  is  held  up.  A  distant  signal  is  of  substantially  the  same  construction,  its  disk  being 
made  of  green  silk  instead  of  red. 


56  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

Fig.  3  shows  the  construction  of  the  signal  instrument  (Z>,  fig.  1);  L  and  the  corre. 
spending  arm  below  it  are  the  two  wings  of  an  armature  which  revolves  on  the  shaft  W 
between  the  prolonged  cores  S  and  T  of  the  electromagnet,  and  to  which  are  attached  the 
disk  D  and  its  counter- weight  rod  C.  The  disk  being  heavier  than  its  counter- weight,  the 
signal  moves  to  danger  by  gravity.  When  the  electromagnet  is  energized  the  disk  is 
drawn  up  out  of  sight  by  the  rotary  movement  of  the  armature. 

Figs.  4  and. 5  show  the  track  instrument,  fig.  5  being  an  enlarged  view  of  the  top 
plate.  The  lever  Z/,  upon  being  depressed  by  the  wheels  of  a  passing  train,  forces  up  the 
piston  JSj  moving  in  an  air  chamber  D,  and  communicates  motion  to  the  key  lever  A 
(fig.  5)  of  the  circuit-closing  apparatus.  The  upper  and  lower  ends  of  the  air  chamber 
are  connected  with  each  other  by  a  port  X,  so  arranged  that  when  the  piston  is  forced 
upward  a  portion  of  the  air  above  the  piston  is  forced  out  through  the  port  X  and  open- 
ing Y,  which  is  placed  a  little  below  the  top  of  the  cylinder.  When  the  piston  has  risen. 


Top  Plate  Track  Instrument— Fig.  5. 

high  enough  to  cover  the  opening  T,  the  communication  with  the  lower  end  of  the  cylin- 
der is  cut  off  and  the  air  remaining  in  the  upper  part  is  confined  and  constitutes  a  cushion, 
preventing  the  piston  rod  from  being  thrown  forcibly  up  against  the  top  cap.  The  piston 
rod  extends  up  through  the  cylinder  head,  or  top  plate,  as  shown  in  fig.  5.  Upon  being 
actuated  by  the  lever  L  its  beveled  top  engages  the  roller  of  the  swinging  arm  A,  which 
forces  the  spring  B  to  a  contact  with  its  anvil  (7,  thus  completing  a  circuit  between  1  and 
2,  the  wire  connections.  When  the  piston  has  been  raised  by  the  action  of  a  passing 
train,  the  air  forced  out  by  it  is  driven  through  the  port  Xand  enters  the  air  chamber  below 
the  piston  ;  so  that  when  it  falls  back  the  air  so  introduced  retards  it  in  its  fall,  thus  pre- 


THE  HALL  BLOCK  SYSTEM.  57 

venting  injurious  shocks.  JR,  is  a  valve  for  regulating  this  air  pressure.  The  lower  end  of 
the  piston  rod  moves  in  a  closed  chamber  J3,  in  which  the  end  of  the  track  lever  works. 
This  opening  is  closed  by  means  of  movable  plates  F,  fixed  on  the  lever  and  working 
against  the  edges  of  the  opening.  The  lever  is  confined  between  two  rubber  springs  Cf 
and  H,  which  are  so  compressed  that  any  weight  less  than  that  imposed  by  the  pressure 
of  an  ordinary  car  wheel  fails  to  operate  the  piston. 

The  Hall  company  provides  a  modification  of  this  system  for  permissive  blocking 
whereby  a  second  train  entering  a  section  before  the  first  has  cleared  it  cuts  out  the  elec- 
tric circuit  from  the  signal  behind  it,  so  that  the  signal  can  be  cleared  only  by  the  last 
train  of  the  series.  This  method  is  used  on  the  New  York  Central  &  Hudson  River,  and 
is  more  fully  described  on  a  succeeding  page. 

The  Hall  signals  have  shown  some  remarkable  records.  For  example,  one  of  the 
earliest  signals  (of  the  latest  form),  located  near  Wellesley  Hills,  Mass.,  on  the  Boston  & 
Albany,  worked  20  months  without  a  fault.  Going  into  service  May  30,  1888,  and  being 
used  as  a  positive  block  signal,  it  has  never  got  out  of  order,  caused  an  unnecessary  stop, 
or  shown  safety  when  danger  existed,  thus  making  a  perfect  mechanical  record.  [Jan. 
24,  1890.]  In  consequence  of  its  satisfactory  operation,  the  Boston  &  Albany  equipped 
the  entire  line  from  Riverside  to  Worcester,  33  miles,  double  track,  with  the  system,  the 
sections  being  overlapped. 

The  New  York,  New  Haven  &  Hartford  uses  the  system  even  more  extensively  than 
the  Boston  &  Albany,  and  now  employs  in  regular  block  service  92  signals,  protecting  all 
station  yards  (also  the  bridge  over  the  Connecticut  River  at  Windsor  Locks,  where  the 
two  main  tracks  are  intervolved),  dangerous  points  and  switches  on  the  main  line  be- 
tween New  Haven  and  Springfield,  64  miles.  A  sample  of  the  records  on  this  road  is  that 
given  by  the  supervisor  of  signals  on  the  Hartford  division,  to  the  effect  that  all  the  sig- 
nals in  his  charge  (92)  (October,  1890)  had  worked  for  38  days  without  an  unnecessary 
stop  or  a  complaint  of  any  kind  from  trainmen. 

For  single-track  working  the  company  provides  electric  interlocking  apparatus,  the 
instruments  being  made  on  the  principle  of  those  used  for  the  Hall  highway-crossing  sig- 
nal. By  a  simple  arrangement  a  train  entering  a  section  sets  a  signal  at  danger  in  the 
rear,  and  at  the  same  time  the  one  at  the  other  end  of  the  section  is  locked  in  the  danger 
position  so  as  to  stop  trains  from  the  opposite  direction. 


HALL    BLOCK    SIGNALS    ON    THE    NEW    YORK    CENTRAL. 

{December  5, 1890.] 

The  automatic  electric  block  system  of  the  Hall  Signal  Company,  which  has  been  in 
use  for  two  or  three  years  on  the  Boston  &  Albany  and  New  York,  New  Haven  &  Hart- 
ford roads,  is  now  in  use  on  an  eight-mile  section  of  the  New  York  Central  &  Hudson  River 
(double  track)  near  Peekskill,  N.  Y.  This  application  is  in  various  respects  more  com- 
plete than  either  of  the  others  mentioned,  and  we  print  herewith  a  diagram  showing  the 
arrangement  of  the  signals  and  giving  a  general  idea  of  the  way  in  which  the  road  has 
been  equipped.  The  portion  of  line  blocked  extends  from  Oscawana  on  the  south  to 
near  Roa  Hook  on  the  north,  8£  miles,  and  there  are  six  blocks  on  the  northbound 
track  and  seven  on  the  southbound.  Each  block  has  a  home  and  a  distant  signal.  All 
switches  within  the  sections  are  equipped  with  a  circuit-breaker,  so  that  whenever  they 
are  moved  off  the  main  track  they  open  the  circuit  and  set  the  signal  for  that  section  at 
"danger."  Each  distant  signal  works  simultaneously  with  its  home  signal. 

As  will  be  seen  by  the  diagram,  the  piece  of  road  blocked  is  quite  crooked,  the 
Peekskill  station  especially  being  in  an  obscure  location.  There  are  short  tunnels  near 
signals  100  and  101  (Oscawana  and  Crugers),  and  there  is  a  drawbridge  in  sections  111 
and  112.  There  is  an  ascending  grade  going  south  from  Peekskill  where  heavy  freight 
Trains  are  liable  to  lose  time,  making  block  signals  specially  needful.  At  Peekskill 
station  there  is  a  grade  crossing  from  which  the  view  is  very  short,  and  in  connection 
with  the  block  system  the  signal  company  has  put  in  bells,  which  seasonably  warn  the 
gate-tender  at  this  crossing  of  the  approach  of  trains. 

The  diagram  can  be  easily  read  if  the  meaning  of  the  four  principal  letters  is  re- 
membered. These  are:  H,  home  signal ;  D,  distant  signal;  B,  "block"  track  instru- 
ment, by  which  a  train  sets  a  signal- at  danger;  C,  "clearing"  track  instrument,  by 
which  a  train  restores  a  signal  to  the  clear  position.  Thus  for  block  No.  100,  D  100  is 
the  distant  and  H  100  the  home  signal ;  when  the  engine  of  a  train  passes  B  100  it  sets 
the  signal  at  danger,  and  when  it  passes  C  100  the  signal  is  restored. 

Track  instrument  B  111  also  sets  a-ringing  bells  W  and  X\  and  B  108  starts  bells 
Y  and  Z ;  these  bells  are  silenced  by  the  passage  of  trains  over  the  track  instruments 
near  them.  The  track  instrument  for  H  107  starts  bell  £,  and  B  104  starts  bell  A. 


HALL  BLOCK  SIGNALS  ON  THE  NEW  YORK  CENTRAL. 


59 


-CH2 


MONTROSE  STATION, 


CRUCERS  ST 
HI01 


HALL  AUTOMATIC  BLOCK    SIGNALS  ON   THE    NEW  YORK 
CENTRAL   &  HUDSON    RIVER    RAILROAD. 


60  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

These  bells  are  stopped  in  the  same  manner  as  the  others.  At  S,  south  of  C  109,  is  a 
private  siding.  The  drawbridge  is  interlocked  not  only  with  signals  111,  112,  but  also 
with  113. 

These  bells,  as  also  those  in  the  gate-tender's  cabin,  are  operated  on  the  same  prin- 
ciple as  that  employed  in  the  automatic  highway-crossing  signal  made  by  this  company, 
which  was  illustrated  in  the  Railroad  Gazette  of  March  28,  1890.  Bells  A,  It,  W,  X,  J, 
Z,  as  will  be  seen  by  reference  to  the  diagram,  ring  continuously  from  the  time  a  train 
approaches  within  a  certain  distance  until  it  reaches  the  bell ;  and  this  ringing  warns 
the  switch-tender  not  to  disturb  the  main  track  in  the  face  of  the  approaching  train. 

When  a  train  goes  into  a  siding  to  wait  for  another  train  to  pass  it,  the  circuit,  which 
would  ordinarily  be  closed  by  the  passage  of  a  train  over  the  clearing  track  instrument 
for  that  section,  is  closed  by  the  conductor  or  trainmen  by  means  of  a  circuit-closer  fixed 
near  the  switch.  The  switches  of  crossover  tracks  are  equipped  in  the  same  manner.  A 
southbound  conductor  arriving  at  Peekskill,  for  instance,  and  wishing  to  go  to  the  freight 
sidings  on  the  east  side  of  the  main  line,  goes  to  the  switch  for  the  crossover  track,  and 
if  he  hears  no  warning  from  bell  Z,  turns  it ;  this  sets  H  108  at  danger.  When  he  has 
returned  to  his  own  track  and  set  the  switch  for  the  main  track  he  uses  the  hand  instru- 
ment (circuit-closer)  to  restore  H  108  to  safety, 

S  110  is  a  special  signal  to  indicate  the  position  of  the  switch  connecting  with  the 
siding  north  of  it.  A  number  of  passenger  trains  whose  trips  end  at  Peekskill  run  in 
upon  this  side  track,  and  the  signal  is  introduced  so  that  they  need  not  run  slowly  all  the 
way  from  signal  108. 

All  these  block  sections  are  equipped  with  auxiliary  circuits,  by  means  of  which 
trains  can  be  run  under  the  permissive  block  system,  and  the  track  instruments  which 
appear  in  the  diagram  without  letters  are  parts  of  this  apparatus.  The  operation  of  the 
permissive  circuits  can  be  explained  in  a  general  way  as  follows:  A  train  enters,  say, 
section  104  ;  sets  H  104  to  danger,  as  the  engine  passes  it,  by  operating  B  104  ;  at  the  same 
time  D  104  goes  to  caution  and  warns  the  following  train  to  slacken  its  speed.  This  second 
train,  finding  H  104  showing  danger,  stops  two,  three  or  five  minutes  (as  the  rule  may  be), 
and  may  then  proceed  cautiously.  When  the  engine  of  the  first  train  reaches  C  102,  this 
track  instrument  (whose  office  is  primarily  to  restore  H  102  to  the  clear  position)  so 
arranges  the  circuits  that  when  the  second  train  passes  B  104  (if  it  does  so  before  the 
first  train  goes  out  of  the  section)  the  pressure  of  its  wheels  on  the  lever  of  B  104  will  pre- 
vent H  104  being  cleared  by  C  104  when  the  first  train  passes  the  latter.  If,  however,  no 
train  is  closely  following,  the  arrangement  of  circuits  produced  by  C  102  is  changed  when 
the  first  train  reaches  C  104,  and  the  original  condition  restored,  so  that  absolute  blocking 
may  be  resumed. 

The  apparatus  for  this  method  of  working  is  not  so  complicated  as  it  would  seem,  and 
it  has  fulfilled  its-  office  perfectly  during  the  two  months  it  has  been  in  use  here.  The 


HALL  BLOCK  SIGNALS  ON  THE  NEW  YORK  CENTRAL.  61 

officers  of  the  road  say  that  the  whole  system  has  worked  very  satisfactorily.  The  only 
unnecessary  stops  have  been  caused  by  trainmen  forgetting  to  clear  signals  after  entering 
side  tracks,  and  by  improper  ad  j  ustment  of  instruments,  due  to  an  inexperienced  inspector. 
This  last  trouble  occurred  only  three  times,  and  these  were  all  during  the  first  week  of 
operation ;  since  that  time  the  apparatus  has  worked  perfectly.  [Dec.  5,  1890.] 


BLACK'S  AUTOMATIC  BLOCK  SIGNAL. 


[January  24, 1890.] 

This  apparatus,  which  has  beeen  in  use  for  two  or  three  years  on  the  elevated  roads 
of  New  York  and  elsewhere,  is  simple  and  strong  in  construction  and  has  been  found 
very  efficient  in  operation.  The  essential  parts  are  shown  in  the  illustrations  herewith. 

Fig.  1  shows  a  plan  and  side  elevation  of  the  track  instrument.    This  consists  of  a 


Fig  4, 


n 

\ L 


J 

\ 

^r 

-=£J- 

«gsTO 

WMM 

iWTO 

^=- 

W^ 

trn 

Fig.  1. 


Fig.  3. 
BLACK'S  AUTOMATIC  BLOCK  SIGNAL. 

lever  placed  just  outside  of  the  rail,  which  is  depressed  by  the  tread  of  the  wheel  pass- 
ing over  it.  This  operates  a  rocking  shaft,  which  is  connected  with  the  ground  connec- 
tion leading  to  the  signal.  As  will  be  seen,  this  connection  from  the  rocking  shaft  to  the 
ground  connection  is  made  by  means  of  a  rod  having  on  one  end  of  it  a  strong  spiral 
spring,  the  object  of  which  is  to  prevent  severe  shocks  to  the  various  parts. 


BLACK'S  AUTOMATIC  BLOCK  SIGNAL. 


Fig.  2  shows  the  standard  form  of  semaphore  signal  as  used  with  this  system  on  the 
Manhattan  Elevated.  The  post,  which  is  of  iron,  supports  a  cast-iron  shield,  behind 
which  the  blade  is  hidden  when  in  the  "all  clear"  position.  This  shield  is  painted  black, 
so  that  safety  is  indicated  by  the  absence  of  the  arm  rather  than  by  its  perpendicular 
position.  The  motion  plate,  by  which  motion  is  transmitted  from  the  line  of  ground  con- 
nection to  the  bell  crank  at  the  foot  of  the  signal  posts,  is  shown  in  fig.  4.  It  will  be  seen 
that  this  motion  plate  provides  for  a  certain  amount  of  change  in 
the  length  of  the  connecttions  from  expansion  and  contraction, 
or  slack.  By  the  use  of  this  device  the  labor  and  care  necessary  S 
to  keep  the  rods  adjusted  has  been  reduced  to  a  minimum.  On 
the  Manhattan  one  man  attends  to  the  inspection  of  54  signals. 

Fig.  3  is  a  diagram,  not  made  to  scale,  showing  in  a  general 
way  the  operation  of  the  apparatus.  A  A  are  levers  operating 
the  connection  to  signal  A.  A  train  moving  from  right  to  left 
has  passed  the  signal  and  has  set  it  to  danger  by  means  of  the 
track  instrument  A,  near  the  signal.  When  the  engine  arrives 
at  the  first  lever  beyond  signal  B  it  sets  signal  B  to  danger, 
and  immediately  after,  at  the  lever  marked  A,  sets  signal  A  at 
clear.  This  is  repeated  throughout  the  system. 

The  length  of  the  blocks  on  the  New  York  Elevated 
through  which  this  system  has  been  operated  is  about  1,700 
feet.  At  the  regular  speed  of  trains  on  the  Manhattan  this 
distance  is  traversed  in  about  47  seconds,  which  is  as  close  to- 
gether as  trains  can  be  run  in  ordinary  service,  this  amount  of 
time  being  generally  required  at  the  terminal  stations  to  detach 
the  engine  and  attach  a  fresh  one  at  the  other  end  of  the  train. 
Discharging  the  passengers  and  taking  in  the  new  load  also 
requires  nearly  a  minute,  although  it  is  often  done  more 
quickly  than  that. 

The  trains  on  the  Manhattan  lines  where  this  signal  is 
used  are  of  nearly  uniform  length  ;  the  invariable  maximum 
is  five  cars  and  an  engine.  Four-car  trains  are  run  a  good  deal,  and  empty  engines  make 
occasional  trips,  but  the  variation  is  immaterial  from  a  signaling  standpoint.  The  signals 
and  track  instruments  are  therefore  made  to  accommodate  the  five-car  trains.  The 
engine  sets  each  signal  to  danger  when  the  rear  car  has  passed  25  feet  beyond  the  signal, 
and  restores  that  signal  to  "all  clear"  when  the  rear  car  has  passed  the  next  one  ;  each 
is  therefore  a  home  signal.  No  permissive  blocking  is  allowed,  but  every  engineman 
must  be  prepared  to  stop  at  the  signal. 

This  apparatus  is  the  invention  of  Mr.  Robert  Black,  Headmaster,  who  has  been 


64  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

connected  with  the  roadway  department  of  the  New  York  elevated  roads  since  they  were 
built.  The  signals  are  now  made  by  the  Black  Automatic  Railway  Block  Signal  Co., 
of  192  Broadway,  New  York  City.  They  are  in  more  or  less  use  on  the  Staten  Island 
Rapid  Transit  road,  the  Kings  County  Elevated  and  the  Brooklyn  Bridge.  The  Man- 
hattan has  a  series  of  32  continuous  block  sections  in  operation  on  the  Sixth  avenue  line 
above  Fifty-ninth  street. 


ILLUMINATED  SEMAPHORE  SIGNALS. 

[March  30,  1888.] 

There  are  many  railroad  men  and  experts  in  signaling  who  believe  that,  all  things 
considered,  the  indications  of  fixed  signals  should  be  by  color  rather  than  position.     In 


Section  on  E  C  D. 


Fig.  1. 
ILLUMINATED    SEMAPHORE     SIGNAL. 


Section  on  A  A. 


the  evolution  of  signals  the  semaphore  form  has  gradually  come  to  be  considered  the- 
best  Ordinarily  this  shows  danger  or  caution  by  day  by  color  and  form  as  well  as  by 
position,  but  the  application  of  this  principle  to  night  signals  is  more  difficult  and  the  use- 
of  color  alone  is  still  almost  universal.  Various  devices  have  been  employed  for  illuminat 


AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 


ing  the  semaphore  blade  so  as  to  get  a  good  position  signal  at  night,  but  they  have  gener- 
ally failed  from  defective  illumination.  When  the  lamp  is  placed  in  front  of  the  signal  it 
is  found  that  the  rays  reflected  are  so  diffused  that  the  semaphore  is  visible  at  so  little 


ILLUMINATED    SEMAPHORE     SIGNAL. 

distance  as  to  be  useless  except  for  yard  purposes  or  other  places  where  trains  are  moved 
but  slowly.     We  show  two  successful  semaphores  designed  to  get  over  these  difficulties. 

UNION  SWITCH  &  SIGNAL  CO.'S  ILLUMINATED  SEMAPHOBE. 

This  may  be  used  as  a  purely  position  signal,  or  in  combination  with  colored  lenses 
as  a  combined  position  and  color  signal.  It  is  the  design  of  "Messrs.  Spicer  and  Schreuder, 
and  has  been  quite  extensively  used.  In  August,  1889,  an  order  was  issued  on  the  Penn- 


ILLUMINATED  SEMAPHORE  SIGNALS.  67 

sylvania  lines  west  of  Pittsburgh  that  illuminated  blades  should  be  used  for  all  new  work, 
and  this  semaphore  has  been  considerably  used  on  those  lines. 

In  fig.  1  the  semaphore  is  shown  as  designed  to  dispense  with  colored  disks,  and  in 
fig.  2  it  is  shown  with  red  and  green  disks  for  a  three-position  signal.  Another  design  is 
also  made  with  only  a  red  disk. 

The  construction  of  this  illuminated  semaphore  is  very  clearly  shown  in  the  illustra- 
tions. The  reflectors  are  shown  at  Jt  R',  etc.  That  in  the  semaphore  arm  is  concave  and 
corrugated,  as  represented  in  fig.  1.  The  reflected  light  is  thrown  forward  through  a  plain 
glass  Or,  32  in.  long  and  2^  in.  wide.  The  divergence  of  the  rays  would  naturally  make 
the  arm  of  light  so  shown  appear  larger  than  the  actual  dimensions  of  the  glass.  The 
glass  is  put  in  with  rubber  packing,  to  diminish  the  chance  of  breaking  The  lamp  L  is 
of  the  same  size  and  power  as  that  used  in  the  ordinary  signal  of  the  Union  Switch  & 
Signal  Co.  At  B  is  shown  a  lense  for  a  back  light  to  let  the  signalman  see  that  the  lamp 
is  burning  and  that  the  signal  goes  to  its  proper  position. 

This  is  a  beautifully  distinctive  signal,  and  cannot  be  confounded  with  any  other 
lights. 


THE  KOYL  PARABOLIC  SEMAPHORE. 

[October  19,  1888.] 

This  semaphore  is  made  by  the  National  Switch  &  Signal  Company.    It  is  the  inven- 
tion of  Prof.  C.  Herschel  Koyl,  formerly  of  Swarthmore  College,  now  connected  with  the 


Plan. 
THE     PARABOLIC    SEMAPHORE. 

National  company.    This  semaphore  has  been  widely  tried  in  the  United  States  and  is 
the  standard  form  used  by  the  makers  of  it  in  their  signaling  work. 

The  reflecting  surface  and  the  frame  which  incloses  it  form  a  longitudinal  section  of 


THE  KOYL  PARABOLIC  SEMAPHORE.  69 

a  paraboloid.  This  is  mounted  in  the  ordinary  casting  which  supports  the  semaphore 
arm,  and  rotates  about  the  axis  in  the  post,  which  is  also  the  axis  of  the  paraboloid,  in 
the  focus  of  which  the  lamp  is  placed.  To  a  front  view  the  semaphore  presents  the 
dimensions  of  5  feet  6  inches  in  length,  from  the  axis  to  the  end  of  the  blade,  and  11 
inches  in  width,  and  has  a  reflector  4  inches  wide  along  the  centre,  from  end  to  end. 

A  reflecting  surface  of  the  form  specified  has  the  property  of  making  parallel  all  rays 
which  fall  upon  it  from  the  focus,  the  consequence  being  that  there  is  sent  along  the 
track  by  this  means  a  continuous  band  or  beam  of  light  of  definite  dimensions.  The 
specification  of  the  patent  also  says,  "in  view  of  the  fact  that  this  band  or  beam  should 
be  of  such  dimensions  that  at  the  conventional  distance  at  which  the  signal  comes  under 
the  observation  of  the  engineer  it  shall  be  wide  enough  to  extend  across  the  track  to 
which  it  is  appropriated,  and  deep  or  broad  enough  to  about  cover  the  observation  por- 
tion of  the  cab  of  the  engine,  it  will  be  found  desirable  to  slightly  modify  both  the  longi- 
tudinal and  transverse  curvature  of  the  paraboloidal  section  which  forms  the  reflecting 
surface,  so  that  at  such  distance  there  will  be  sufficient  divergence  of  the  rays  to  produce 
a  beam  of  the  dimensions  indicated.  To  accomplish  this  result,  however,  the  modifica- 
tion in  form  of  the  reflector  need  be  very  slight,  and  it  remains  to  all  intents  and  pur- 
poses of  the  contour  of  the  section  of  a  paraboloid." 

The  object  has  been  to  concentrate  upon  the  track  all  the  light  from  the  arm,  and 
then  to  diverge  it  only  so  much  as  the  necessities  of  the  case  may  require,  the  method 
adopted  for  diverging  it  being  to  slightly  corrugate  the  reflector  at  right  angles  to  the 
four  directions  in  which  the  divergence  is  required. 

The  result  is  a  semaphore  which  presents  the  same  appearance  by  day  and  by  night, 
which  combines  the  excellencies  of  a  color  signal  with  those  of  a  position  signal.  The 
upper  half  of  the  lamp  being  red  or  green  and  the  lower  part  clear,  the  arm  when  hori- 
zontal appears  red  or  green,  and  when  dropped  white. 

The  reflecting  surface  is  now  made  of  aluminum,  which  is  lighter  than  glass,  tough 
and  does  not  tarnish. 


THE    STEWART-HALL   TRAIN    ORDER    SIGNAL. 

[January  23, 1891.] 

The  diagram  printed  herewith  shows  the  arrangement  of  wires  and  electromagnets 
used  in  a  train  order  signal  recently  patented  by  Robert  Stewart,  Superintendent  of 
Telegraph  of  the  Central  of  New  Jersey,  and  W.  P.  Hall,  President  of  the  Hall  Signal 
Company.  The  special  features  of  the  signal  are,  1,  that  it  works  entirely  by  electricity, 
so  that  it  can  be  placed  in  the  most  convenient  location,  and  not  necessarily  in  front  of 
the  office ;  and,  2,  a  provision  against  letting  a  train  pass  while  there  are  orders  for  it, 
through  the  operator's  forgetful  ness.  As  is  well  known,  the  last  mentioned  purpose  is 


THE    STEWART-HALL    ELECTRIC    TRAIN     ORDER    SIGNAL. 
Arrangement  of  Instruments  and  Wires. 

appreciated  by  practical  superintendents  and  dispatchers,  and  various  devices  have  been 
heretofore  invented  for  accomplishing  it.  The  convenience  of  locating  the  signal  itself 
some  distance  beyond  the  station,  so  that  a  train  can  be  held  for  orders,  while  at  the  same 
time  permitting  it  to  stop  where  passengers  or  freight  can  be  discharged  and  the  tank 
filled  with  water,  is  obvious.  This,  of  course,  requires  two  signals,  one  for  movements 
in  each  direction.  The  out-door  signal  may  be  either  the  Hall  disk  signal  as  used  in  the 
block  system  of  this  company  or  the  semaphore  shown  below. 

The  electromagnet  $,  in  fig.  1,  represents  the  signal  instrument,  the  presence  of  the 
electric  current  in  the  coils  holding  the  signal  in  the  safety  position  as  shown.  D  rep- 
resents the  "drop,"  which  is  mounted  in  a  cabinet  fixed  at  some  place  in  the  office 


THE  STEWART-HALL  TRAIN  ORDER  SIGNAL. 


71 


where  the  operator  must  leave  his  desk  in  order  to  reach  it.     It  will  be  seen  that  when- 
ever the  circuit  is  opened  the  armature,  in  falling  away,  opens  its  own  circuit  in  such  a 
way  that  it  can  be  again  closed  only  by  lifting  the  armature  of  D 
by  hand.    As  will  be  seen  in  fig.  2,  this  armature  carries  a  tablet 
lettered  so  .as  to  warn  the  operator  of  the  fact  that  a  train  order  is 
on  hand.     The  opening  of  the  circuit  permits  this  tablet  to  fall 
from  its  hidden  position  to  a  stop  which  leaves  it  in  front  of  a 
glass-covered  opening  in  the  case. 

On  receiving  an  order  for  a  train  the  operator  sets  the  signal 
at  danger  by  opening  the  switch  CY,  which  is  located  on  his  desk. 
If  now,  when  the  train  arrives,  he  should  forget  that  he  is  to 
stop  it,  and  should  attempt  to  clear  the  signal  by  closing  the 
key  (7,  he  would  find  that  the  signal  remained  at  danger,  and,  on 
going  to  the  cabinet  D,  to  close  the  circuit  by  lifting  the  armature, 
would  be  reminded  by  the  tablet  of  the  presence  of  the  train 
order.  The  lifting  of  the  armature  is  accomplished  by  means  of 
a  large  push  button  or  plunger,  and  this  button  can  be  arranged 
with  a  clip  to  receive  a  folded  order,  so  that  the  circuit  cannot 
conveniently  be  closed  without  first  picking  up  the  order. 

Two  of  these  signals  have  been  erected  at  Somerville,  14.  J., 
on  the  Central  of  New  Jersey,  one  for  westbound  and  one  for 
eastbound  trains,  and  additional  applications  are  now  being  made 
on  this  and  other  roads. 

THE    HALL    ILLUMINATED     ELECTRIC     SEMAPHORE. 

In  connection  with  the    train  order  signal  described  above, 
the  Hall  company  uses  the  new  form  of  semaphore  shown  in  the 
accompanying  cut.     The  mechanism  for  operating  this  signal  is 
precisely  the  same  as  that  used  in  the  disk  signal.     In  the  disk 
signal  the  counterweight  is  lighter  than  the  signal,  but  in  the 
semaphore  it  is  made  heavier  so  that  the  arm  shall  assume  the 
horizontal  position  in  case  of  failure  of  the  circuit  or  operator. 
The  cut  shows   the  signal  as   actually  used  at   Somerville,  the1 
case  being  a  modification  of  the  pattern  used  for  disk  signal  ;TheHall  Electric  Semaphore. 
but  the  company  is  making  plans  for  a  case  with  a  glass-covered 

opening  of  a  different  shape.     With  a  rectangular  opening  of  the  right  proportions  the 
ordinary  semaphore  can  be  quite  closely  imitated,  the  side  of  the  case  answering  for 


72  AMERICAN  PRACTICE  IN  BLOCK  SIGNALING. 

the  post.    The  angle  shown  by  the  dotted  line  in  the  cut  does  not  indicate  the  limit 
of  the  power  of  the  magnet. 

The  opening  in  the  case,  which  furnishes  a  light  background  for  the  dark  blade,  is 
covered  with  transparent  glass  in  front,  and  with  ground  or  painted  glass  at  the  back. 
The  lamp  for  illuminating  the  signal  at  night  is  placed  18  inches  or  more  away  from  the 
case,  and  is  fitted  with  a  reflector  shaped  to  diffuse  the  rays  of  light  equally  over  the 
whole  surface  of  the  glass.  The  blade  is  made  of  silk  or  cloth  stretched  on  a  hollow 
wire,  the  same  as  the  Hall  disc,  and  is  therefore  sufficiently  translucent  to  show  its  color 
at  night.  It  can  be  made  of  any  desired  color  that  contrasts  sufficiently  with  white. 


W.LLIAM   P.   HALL,  President.  A.  W.  HALL,  General  Manager. 

W.  S.  GILMORE,  Treasurer.  S.  MARSH  YOUNG,  General  Agent. 

THE   HALL  SIGNAL   COMPANY 

5O  Broadway,  New  York.  34O  The  Rookery,  Chicago. 

MANUFACTURERS    OF 

All  Kinds  of  Electric  Signaling  Apparatus 

FOR    RAILROADS. 

The  Hall  Automatic  Electric  Block  Signal  System, 

The  Hall  Highway-Crossing  Alarm  Bell, 

The  Stewart- Hall  Electric  Train-Order  Signal, 

The  Hall  System  of  Interlocking  Signals  for  Grade  Crossings  of  One 

Railroad  with  Another. 

ELECTRIC      DISTANT      SIGNALS      FOR      SWITCHES. 

The  Hall  apparatus,  described  in  the  foregoing  pages  of  this  volume,  is,  as  the  title  of  the  book  implies,  prin- 
cipally that  used  for  block  signaling.  The  chapter  devoted  to  the  Hall  system  in  the  first  part  of  the  book  (a 
reprint  of  an  article  in  the  Railroad  Gazette)  will  be  found  to  be  couched  in  the  conservative,  cautious  and  con- 
densed language  usually  found  in  an  editorial,  and  it  was,  moreover,  written  in  connection  with  articles  about 
other  systems  of  signaling,  which  circumstance  led  the  writer  to  treat  some  points  in  a  manner  not  conducive  to 
the  best  understanding  of  this  particular  system.  The  descriptions  of  the  Hall  apparatus  in  the  appendix  like- 
wise suffered  from  editorial  limitations  both  in  text  and  illustration,  and  do  not  give  an  adequate  idea  of  the 
completeness  of  our  system  or  of  its  adaptability  to  all  the  demands  of  perfect  railroad  service.  While  finding  no 
fault  with  the  publishers  for  this  condition  of  things,  we  have  concluded  that  the  best  use  we  can  make  of  these 
advertising  pages,  will  be  to  lay  before  the  reader  a  few  additional  facts,  which,  by  supplementing  the  illustrated 
descriptions  and  other  matter,  will  give  him  a  more  complete  idea  of  what  we  can  do  and  are  doing.  These 
facts,  with  some  reference  to  the  evidence  that  we  can  show  to  those  unacquainted  with  our  systems  to  prove 
our  claims,  will  be  found  on  the 

NEXT    PAGE. 


THE    HALL   HIGHWAY   CROSSING    SIGNAL 
is  described  on  page  3. 


THE  HALL  SIGNAL  COMPANY. 


[Advertisement.  ] 


THE   HALL  ELECTRIC  AUTOMATIC  BLOCK-SIGNAL  SYSTEM. 


By  the  above  term  is  meant  the  Hall  system  with  a 
wire  upon  poles  and  the  Hall  disk  signal,  as  shown  in 
the  descriptions  in  this  book.*  To  profitably  read  those 
descriptions  the  reader  should  first  fix  in  his  mind 
some  of  the  essential  conditions  of  block  signaling. 

The  main  features  demanded  in  an  automatic  block 
signal  are  well  known.  They  are :  that  it  shall 
promptly,  on  the  passage  of  a  train,  change  from 
safety  to  danger,  and  thus  protect  the  train  against  a 
rear  collision  until  it  shall  have  passed  beyond  another 
signal  further  on;  that  the  signal  shall  instantly  go  to 
danger  whenever  a  switch  is  turned  to  the  side  track, 
and  that  it  shall  perform  these  operations  unerringly ; 
that  the  changing  from  danger  back  to  safety  after  the 
train  moves  out  of  the  block  section  shall  be  done 
promptly,  and  that  failures  to  do  this,  and  other  fail- 
ures (which,  while  not  dangerous,  cause  delays  to 
trains  and  other  annoyances)  shall  be  reduced  to  a 
satisfactory  minimum.  These  points  are  set  forth  at 
length  in  our  illustrated  catalogue,  which  is  already 
familiar  to  most  railroad  operating  officers.  Ihe 
Hall  signal  meets  all  th°.se  conditions.  The  vital 
question  is,  can  trams  be  run  close  together  with 
safety,  regularity  and  convenience.  The  first 
trouble,  where  trains  follow  each  other  closely,  is 
that  the  detention  of  one  by  a  signal  that  fails  to 
operate  detains  a  number  of  others.  This  empha- 
sizes the  demand  for  perfect  apparatus  and  con- 
stant, intelligent  care.  The  satisfactory  way  in  which 
the  Hall  signals  meet  this  test  is  beyond  comparison 
with  the  showing  made  by  any  other  automatic  signal. 
The  good  records  from  a  few  roade,  shown  in  our  illus- 
trated catalogue  published  a  year  ago,  are  now  re- 
peated on  a  number  of  others,  and  in  localities  where 
the  service  is,  if  possible,  more  exacting.  These  rec- 
ords will  be  given  in  detail  to  railroad  officers  inter- 
ested. As  most  interested  readers  know,  it  is  next  to 
impossible  to  maintain  gJod  discipline  among  engi- 
neers where  they  are  frequently  stopped  by  signals  un- 
necessarily—that is,  where  there  is  some  fault  in  the 
battery  or  connections,  or  something  else  that  has  re- 
sulted from  carelessness;  and  a  signal  which  thus 
causes  annoyance  is,  in  some  respects,  as  undesirable 
as  one  with  worse  faults.  Our  records  will  show  that 
the  number  of  these  unnecessary  stops  can  be,  and  is, 
kept  very  much  smaller  with  the  Hall  than  with  any 


other  automatic  signal.  There  is  no  mystery  about 
this.  The  explanation  is  found  in  the  greater  simplicity 
of  the  apparatus  and  the  superior  mecnanical  construc- 
tion of  everything  connected  \\ita  the  system.  Bat- 
teries can  be  kept  up  by  ordinarily  intelligent  men. 
The  detection  of  bad  connections,  wrong  adjustments, 
and  other  troubles  is  not  such  an  intricate  job  as  to  re- 
quire an  expert  with  elaborate  training.  We  insist  on 
good  men,  and  require  faithful  service,  but  we  do  not 
ask  impossibilities  of  them.  A  chief  trouble  with 
track-circuit  signals  is  that  the  faults  of  the  system,  of 
the  apparatus,  and  of  the  men,  when  all  combined 
make  up  such  an  aggregate  of  delays,  annoyances  and 
dangers  that  they  are  intolerable.  The  system  de- 
mands delicate  battery  power  which  must  be  very 
carefully  adjusted;  and  even  then  wet  weather  will 
often  baffle  the  best  attempts  at  adjustment  of  the  in- 
struments. A  vital  feature  of  the  system  is  the  shunt, 
by  which  the  current,  when  the  signal  is  to  be  set  at 
danger,  is  not  wholly,  but  only  partially,  withdrawn 
from  the  signal  magnet.  This  is  a  feature  which  prob- 
ably can  never  be  made  to  work  with  the  simplicity 
and  certainty  of  a  good  wire  circuit  system  in  which 
the  circuit  is  positively  and  totally  broken  every  time 
a  train  enters  the  section.  As  to  construction  of  appa- 
ratus the  Hall  Signal  Company  only  ask  a  compari- 
son of  their  goods  with  those  of  any  other  manufacturer. 
The  opinions  of  railroad  officers  who  have  used  our  in- 
struments and  others  side  by  side  will  be  freely  shown. 
As  to  negligence  of  inspectors,  the  Hall  Signal  Com- 
pany expects  human  fallibility,  and,  as  above  inti- 
mated, only  demands  good,  intelligent  men,  managed 
with  reasonable  discipline.  All  we  have  to  say  is  that 
such  men  have  succeeded  in  regularly  making  satisfac- 
tory records.  The  company's  standing  offer  to  guaran- 
tee the  maintenance  of  signals  forfivt  years  at  a  fixed 
low  rate  per  year  should  be  sufficient  confirmation  of 
this;  but  we  do  not  ask  roads  using  our  signals  to  put 
up  with  a  mere  guarantee,  for  we  f ally  recognize  that 
a  money  forfeit  would  be  poor  compensation  for  an  un- 
satisfactory signal  system;  and  inspection  of  signals  in 
satisfactory  operation  on  prominent  roads  is  earnestly 
invited.  We  desire  railroad  officers  to  convince  them- 
selves of  the  merits  of  our  system.  The  complaint 
about  the  deceptions  of  selling  agents  shall  not  be 
justly  applied  to  the  Hall  signals. 


*  We  own  the  best  patents  on  rail  circuit  systems  and  contract  to  put  in  such  systems  with  apparatus  possessing  all  the 
mechanical  perfection  which  has  so  long  characterized  the  work  of  our  shops.  This  is  now  practicable  in  consequence  of  the 
expiration  of  patents  which  formerly  kept  this  company— or  rather'  its  predecessor— out  of  this  field.  We  also  make  semaphore 
signals,  both  inclosed  in  acase  with  a  glass-covered  opening,  and  uninclosed;  but  the  present  chapter  is  devoted  to  the  Hall  sys- 
tem, as  it  is  now  most  largely  used- 


[Advertisement.} 


THE    HALL   SIGNAL   COMPANY. 


AUTOMATIC     HIGH  W  AY-CROSSING     SIGNALS. 


The  heavy  expense  involved  in  keeping  watchmen 
at  road  crossings  makes  a  reliable  automatic  apparatus 
for  warning  travelers  an  important  desideratum  ;  but 
most  superintendents  have 
had  their  faith  in  auto- 
matic bells  seriously  weak- 
ened, if  not  destroyed,  by 
the  very  poor  service  given 
by  the  devices  heretofore 
made  and  sold.  The  Hall 
bells  give  perfect  satisfac- 
tion. This  is  a  sweeping 
statement,  but  it  is  based  on 
the  testimony  of  intelligent 
and  conservative  railroad 
officers.  The  apparatus  is 
simple  and  of  the  best  de- 
sign, and  carefully  made. 
The  first  cost  is  somewhat 
higher  than  that  of  other 
makes,  but  the  freedom 
from  annoyances  soon  over- 
balances that,  while  a  bell 
which  fails  to  ring  when  a 
train  is  approaching,  and 
persists  in  ringing  when  a 
train  is  not  coming,  is  dear 
at  any  price.  The  Hall  bell 
is  operated  by  the  simple 
and  reliable  interlocking 
magnets  used  in  our  single- 
track  block  signals  (de- 
scribed on  a  succeeding 
page),  these  in  turn  being 
actuated  by  the  Hall  track 
instruments.  The  bell  be- 
gins to  ring  when  the  train 
passes  the  track  instrument, 
and  continues  to  ring  until 
the  train  reaches  the  cross- 
ing, whether  the  interven- 
ing time  be  short  or  long. 
By  a  simple  arrangement 
of  interlocking  instruments 
and  track  instruments,  the  bell  is  made  to  ring  by  the 
approach  of  a  train  from  either  direction  on  a  single 
track,  the  track  instrument  which  would  cause  a 


AUTOMATIC   CROSSING    SIGNAL. 
The  gong  is  covered  by  the  circular  wire  screen. 


false  signal  by  being  operated  by  a  train  moving 
away  from  the  crossing  instead  of  toward  it, 
being  automatically  cut  out. 

The  experience  of  this 
company  has  shown  that 
an  open  circuit  Is  the 
most  desirable  in  all  re- 
spects for  the  operation  of 
a  signal  of  this  kind.  The 
primary  reason  for  using 
a  closed  circuit— that  the 
failure  of  a  battery  or 
wire  shall  automatically  re- 
veal itself — is  found  to  be 
practically  valueless  in  a 
highway  -  crossing  signal ; 
and,  in  view  of  the  reduc- 
tion in  first  cost  of  wires, 
instruments  and  battery, 
and  of  expense  for  battery 
material  and  maintenance, 
as  .well  as  the  labor  of 
taking  care  of  the  signals, 
the  open-circuit  system  is 
far  preferable.  The  records 
of  the  operation  of  these 
signals  on  the  many 
railroads  using  them  are 
such  as  to  substantiate 
these  statements.  The  bell 
as  used  for  highway  cross- 
ing signals  is  also  used 
with  much  satisfaction  at 
crossings  where  gates,  with 
an  attendant,  are  main- 
tained. The  certainty  of 
its  operations  make  it  a  re- 
liable indicator  by  which 
the  gate-tender  may  be  noti- 
fied so  as  to  always  close 
the  gates  in  proper  season 
before  the  arrival  of  a  train; 
and  where  travelers  on 
the  highway  are  familiar 
with  the  locality  the  bell  will  serve  as  a  warn- 
ing to  them  at  night  when  the  attendant  is  off 
duty. 


THE  HALL  SIGNAL  COMPANY. 


[Advertisement.] 


ELECTRIC     INTERLOCKING     INSTRUMENT. 


The  highway  crossing  bell  is  operated  by  means  of 
the  interlocking  instrument  shown  on  the  opposite 
page.  When  approaching  trains  strike  the  first  track 
instrument  they  lock  the  advancing  and  retreating 
springs  in  one  position,  which  sets  the  bell  ringing,  and 
when  the  wheels  strike  the  track  instrument  at  the 
crossing  the  springs  are  instantly  thrown  to  the  other 
position,  cutting  off  the  current  from  the  bell. 

This  instrument  consists  principally  of  a  main  elec- 
tro-magnet A  and  its  armature,  and  an  unlocking 
electro-magnet  B  and  its  armature,  the  latter  consti- 
tuting a  locking  lever.  To  the  armature  of  A  is  fast- 
ened a  horizontal  bar  which,  by  means  of  tappets, 
actuates  the  advancing  spring  C  and  the  retreating 
spring  7).  When  the  main  electro-magnet  is  momen- 
tarily energizedjind  its  armature  attracted,  contact  is 

spring  C  and  its  anvil  c, 


while  the  contact  between  retreating  spring  D  and  its 
anvil  d  is  broken.  The  armature  of  B  instantly  drops, 
locking  the  armature  of  A  and  retaining  the  springs  in 
this  position.  When  B  is  momentarily  energized  and 
its  armature  attracted,  the  armature  of  A  is  unlocked 
and  contact  is  made  between  retreating  spring  D  and 
its  anvil  d,  while  the  contact  between  advancing 
spring  C  and  its  anvil  c  is  broken.  Thus,  when  the 
advancing  spring  is  open  the  retreating  spring  must  be 
closed,  and  when  the  retreating  spring  is  open  the  ad- 
vancing spring  must  be  closed.  Upon  this  principle  is 
based  the  Hall  System  of  Electric  Interlocking. 

These  instruments  are  also  used  in  single-track  block 
signaling,  in  signals  for  the  protection  of  grade  cross- 
ings (of  one  railroad  with  another),  and  in  signals  for 
the  protection  of  single  or  double  track  junctions. 


[Advertisement.  ] 


THE  HALL  SIGNAL  COMPANY. 


INTERLOCKING     INSTRUMENT. 


THE    HALL    SIGNAL    COMPANY. 


[Advertisement  ] 


THE    HALL    TRACK    INSTRUMENT. 


This  instrument,  shown  in  the  illustrated  description 
of  the  Hall  block  signal,  is  of  such  general  adaptability 
that  it  is  used  for  any  and  every  situation  where  it  is 
desired  to  have  a  train  open  or  close  an  electric  circuit. 
This  is  the  only  device  of  the  kind  that  has  ever  given 
satisfactory  service  for  any  length  of  time.  It  has 
been  in  use  for  many  years  (though  recently  improved) 


and  has  withstood  the  hardest  service  with  exceedingly 
small  expense  for  care  and  repairs.  The  combination 
of  rubber  and  air  cushions  for  absorbing  all  shocks 
gives  it  great  durability  and  prevents  all  objectionable 
noise,  a  feature  that  will  be  appreciated  by  those 
familiar  with  the  clanging  produced  by  some  kinds  of 
track  levers. 


DISCS    AND    INCLOSED     SIGNALS. 


The  Hall  disc  signal  has  been  objected  to  in  certain 
quarters  because  it  lacks  some  of  the  distinctive  fea- 
tures of  the  ordinary  out-door  semaphore  ;  but  there 
are  advantages  in  its  present  form  which  each  year's 
use  makes  more  apparent.  One  of  the  first  points 
mentioned  in  favor  of  semaphores  is  that  they  can  be 
seen  great  distances;  but  this  advantage  is  often  neu- 
tralized by  locating  the  signal  where  it  has  a  very  poor 
background,  while  in  other  cases  the  post  is  made  so 
high  (with  a  view  to  rendering  it  visible  at  a  long  dis- 
tance) that  engineers,  keeping  their  eyes  on  the  signal, 
overlook  a  caboose  directly  in  front  of  them  and  run 
into  it.  This  has  occurred  repeatedly.  The  Hall  sig- 
nal case  provides  a  uniform  background  for  every 
signal.  This  makes  even  a  small  disc  more  effective 
than  a  large  semaphore,  as  the  background — that  is, 
the  outline  of  the  case — attracts  the  eye  as  quickly  as 
would  a  semaphore.  The  signal  is  generally  only 
about  12  ft.  above  the  ground,  and  therefore  in  the 
line  easily  and  naturally  followed  by  the  engineer's 
eye.  Men  will  not  overlook  a  red  tail  light  while  look- 
ing for  the  signal.  The  main  object  in  placing  signals 
on  tall  poles — to  give  engineers  warning  at  a  point  a 
long  distance  in  advance  of  the  stopping  place — is 
better  secured  by  the  erection  of  an  auxiliary  (distant) 
signal.  In  foggy  weather,  or  other  obscure  conditions, 
a  ve»y  tall  signal  is  no  better  than  one  of  moderate 
height ;  while  in  clear  weather  there  is  no  necessity 
for  it  at  all  except  to  get  a  good  background,  and  that 
the  Hall  signal  has  in  any  position.  As  will  be  seen 
by  the  description  of  the  Hall  electric  semaphore,  we 
combine  the  advantages  of  a  semaphore  with  those 
of  an  inclosed  signal  (with  a  good  background) 
when  desired. 

It  may  seem  like  a  commonplace  argument  to  men- 


tion here  the  superior  economy  found  in  maintaining 
and  operating  inclosed  signals,  as  compared  with  any 
automatic  signal  exposed  to  wind,  snow  and  rain  ;  but 
when  one  takes  a  broad  view  of  the  matter  this  is 
really  a  more  important  point  than  it  seems,  for  it 
reaches  into  all  the  future  years  that  the  signal  may 
be  used.  Indeed,  the  persistent  success  of  our  inclosed 
signals,  in  spite  of  the  disadvantages  (after  all,  mostly 
theoretical)  they  have  been  believed  to  labor  under, 
has  been  largely  owing  to  this  favorable  feature.  If 
an  automatic  signal  is  to  work  outdoors  in  spite  of  the 
elements,  it  must  have  a  large  reserve  power ;  where  a 
force  of  10  Ibs.  is  ordinarily  needed,  50  Ibs.  or  100  Ibs. 
must  be  provided  to  allow  for  variation  in  weight, 
wind  pressure  and  other  uncertain  factors.  Now,  this 
necessity  for  additional  power  is  responsible  for  most 
of  the  inevitable  complications  and  added  expense. 
The  task  of  keeping  in  order  a  Hall  inclosed  signal 
may  be  compared  to  that  imposed  upon  an  operator  in 
charge  of  a  simple  Morse  telegraph  instrument,  which 
is  almost  nil  as  far  as  skill  and  time  are  concerned  ; 
while  every  outdoor  automatic  signal  thus  far  tried 
has  be*en  made  to  give  'passable  service  only  by  being 
subjected  to  constant  experiments,  changes  of  plan 
and  of  apparatus,  and  other  expedients  ;  and  after  10 
years'  trial  the  prospect  of  a  satisfactory  outcome  is 
no  better  than  at  the  start.  In  presenting  this  aspect 
of  the  case  we  may  possibly  seem  to  be  "  retarding  the 
progress  of  science  ";  but  our  labors  to  provide  for  rail- 
roads (1)  just  such  signal  apparatus  as  the  service  needs, 
and  (2)  such  as  will  do  what  it  seems  to  do,  will  attest 
to  all  conversant  with  the  facts  that  we  are  not  un- 
progressive.  It  is  only  by  constantly  considering  both 
of  the  above  factors  that  any  real  progress  can  be 
attained. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 

_      -._      .  STAMEED  BELOW 
•L              ^%   I           ^^^ 

l\ltW^AAl|ff[NE  OF  25  CENTS 

•  WrLLTBE^sWffsED   FOR   FAILURE  TO   RETURN 
THIS   BOOK   ON   THE   DATE  DUE.   THE   PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY    AND    TO     $I.OO    ON    THE    SEVENTH     DAY 
OVERDUE. 

MAO     Q   1941  M 

SENT  ON  ILL 

ninn    O    iCF*ti  iii 

P 

JUL  2  3  W7 

U.C.  BERKELEY 

1       180rf8tLV 

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JUL  5     OTJ 

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KC.  C1R.    APR  i  8  1981 

MAO  A    A    tA^M     L 

WAK  2  »  f9$#  4 

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LD  21"100m-7,'39(402s 

YD   17819 


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